Another random segfault, this time happening in `ByteString(Object)>shallowCopy`.

Steps to reproduce: unknown.

Stacktrace ([Full Travis log](https://travis-ci.org/hpi-swa-teaching/SWT18-Project-13/jobs/396783693#L131)): ``` Smalltalk stack dump: 0xbff69e1c M ByteString(Object)>shallowCopy 0x4b0c8a8: a(n) ByteString 0xbff69e34 M ByteString(Object)>copy 0x4b0c8a8: a(n) ByteString 0xbff69e4c M ByteString(String)>withSqueakLineEndings 0x4b0c8a8: a(n) ByteString 0xbff69e64 M MCMethodDefinition>initializeWithClassName:classIsMeta:selector:category:timeStamp:source: 0x1df45a0: a(n) MCMethodDefinition 0xbff69e98 M MCMethodDefinition class>className:classIsMeta:selector:category:timeStamp:source: 0x26f3520: a(n) MCMethodDefinition class 0xbff69eec M [] in MCFileTreeStCypressReader>addMethodDefinitionsForClass:methodProperties:in:extensionMethod: 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff69f10 M [] in MultiByteFileStream class(FileStream class)>detectFile:do: 0x308eac0: a(n) MultiByteFileStream class 0xbff69f30 M BlockClosure>ensure: 0x1df47f8: a(n) BlockClosure 0xbff69f50 M MultiByteFileStream class(FileStream class)>detectFile:do: 0x308eac0: a(n) MultiByteFileStream class 0xbff69f70 M MultiByteFileStream class(FileStream class)>readOnlyFileNamed:do: 0x308eac0: a(n) MultiByteFileStream class 0xbff69f90 M UnixFileDirectory(FileDirectory)>readOnlyFileNamed:do: 0x1df4930: a(n) UnixFileDirectory 0xbff69fb0 M DirectoryEntryFile>readStreamDo: 0x1df4970: a(n) DirectoryEntryFile 0xbff69fdc M [] in MCFileTreeStCypressReader>addMethodDefinitionsForClass:methodProperties:in:extensionMethod: 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6a000 M Array(SequenceableCollection)>do: 0x1df4ab8: a(n) Array 0xbff6a02c M [] in MCFileTreeStCypressReader>addMethodDefinitionsForClass:methodProperties:in:extensionMethod: 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6cdf8 M Array(SequenceableCollection)>do: 0x1df5208: a(n) Array 0xbff6ce14 M MCFileTreeStCypressReader>addMethodDefinitionsForClass:methodProperties:in:extensionMethod: 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6ce3c M MCFileTreeStCypressReader>addMethodDefinitionsForClass:methodProperties:in: 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6ce74 M MCFileTreeStCypressReader>addClassAndMethodDefinitionsFromEntry: 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6ce90 M [] in MCFileTreeStCypressReader>addClassAndMethodDefinitionsFromDirectory: 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6ceb4 M Array(SequenceableCollection)>do: 0x1df5428: a(n) Array 0xbff6ced0 M MCFileTreeStCypressReader>addClassAndMethodDefinitionsFromDirectory: 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6cef4 M MCFileTreeStCypressReader>loadDefinitions 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6cf14 I MCFileTreeStCypressReader(MCVersionReader)>definitions 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6cf38 I MCFileTreeStCypressReader(MCVersionReader)>snapshot 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6cf68 I MCFileTreeStCypressReader>basicVersion 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6cf80 M MCFileTreeStCypressReader(MCVersionReader)>version 0x1df4660: a(n) MCFileTreeStCypressReader 0xbff6cf98 M [] in MCFileTreeRepository(MCFileBasedRepository)>loadVersionFromFileNamed: 0x4896708: a(n) MCFileTreeRepository 0xbff6cfc8 I [] in MCFileTreeRepository(MCFileBasedRepository)>versionReaderForFileNamed:do: 0x4896708: a(n) MCFileTreeRepository 0xbff6cfe4 M MCFileTreeRepository>readStreamForFileNamed:do: 0x4896708: a(n) MCFileTreeRepository 0xbff6d00c I MCFileTreeRepository(MCFileBasedRepository)>versionReaderForFileNamed:do: 0x4896708: a(n) MCFileTreeRepository 0xbff6d02c M MCFileTreeRepository(MCFileBasedRepository)>loadVersionFromFileNamed: 0x4896708: a(n) MCFileTreeRepository 0xbff6bddc M [] in MCFileTreeRepository>goferVersionFrom: 0x4896708: a(n) MCFileTreeRepository 0xbff6be0c M Array(SequenceableCollection)>collect: 0x1df4d50: a(n) Array 0xbff6be28 M MCFileTreeRepository>goferVersionFrom: 0x4896708: a(n) MCFileTreeRepository 0xbff6be4c I MetacelloCachingGoferResolvedReference(GoferResolvedReference)>version 0x1df4c80: a(n) MetacelloCachingGoferResolvedReference 0xbff6be64 M MetacelloCachingGoferResolvedReference>version 0x1df4c80: a(n) MetacelloCachingGoferResolvedReference 0xbff6be7c M [] in MetacelloFetchingMCSpecLoader>resolveDependencies:nearest:into: 0x48ced80: a(n) MetacelloFetchingMCSpecLoader 0xbff6be9c M OrderedCollection>do: 0x1df4de8: a(n) OrderedCollection 0xbff6bec8 M [] in MetacelloFetchingMCSpecLoader>resolveDependencies:nearest:into: 0x48ced80: a(n) MetacelloFetchingMCSpecLoader 0xbff6bee4 M BlockClosure>on:do: 0x1df4e98: a(n) BlockClosure 0xbff6bf0c M MetacelloFetchingMCSpecLoader>resolveDependencies:nearest:into: 0x48ced80: a(n) MetacelloFetchingMCSpecLoader 0xbff6bf4c M [] in MetacelloFetchingMCSpecLoader>linearLoadPackageSpec:gofer: 0x48ced80: a(n) MetacelloFetchingMCSpecLoader 0xbff6bf68 M [] in MetacelloSqueakPlatform>do:displaying: 0x4067c78: a(n) MetacelloSqueakPlatform 0xbff6bf90 M [] in MorphicUIManager>displayProgress:at:from:to:during: 0x277f388: a(n) MorphicUIManager 0xbff6bfac M BlockClosure>on:do: 0x1df5078: a(n) BlockClosure 0xbff6bfd8 M [] in MorphicUIManager>displayProgress:at:from:to:during: 0x277f388: a(n) MorphicUIManager 0xbff6bff8 M BlockClosure>ensure: 0x1df5170: a(n) BlockClosure 0xbff6c01c M MorphicUIManager>displayProgress:at:from:to:during: 0x277f388: a(n) MorphicUIManager 0xbff5dca0 M ProgressInitiationException>defaultResumeValue 0x1df4280: a(n) ProgressInitiationException 0xbff5dcbc M ProgressInitiationException(Exception)>resume 0x1df4280: a(n) ProgressInitiationException 0xbff5dcd4 M ProgressInitiationException>defaultAction 0x1df4280: a(n) ProgressInitiationException 0xbff5dcf0 M UndefinedObject>handleSignal: 0x2375b00: a(n) UndefinedObject 0xbff5dd14 M MethodContext(ContextPart)>handleSignal: 0x4897410: a(n) MethodContext 0xbff5dd38 M MethodContext(ContextPart)>handleSignal: 0x45468a8: a(n) MethodContext 0xbff5dd5c M MethodContext(ContextPart)>handleSignal: 0x490d428: a(n) MethodContext 0xbff5dd80 M MethodContext(ContextPart)>handleSignal: 0x490d488: a(n) MethodContext 0xbff5dda4 M MethodContext(ContextPart)>handleSignal: 0x490d4e8: a(n) MethodContext 0xbff5ddc8 M MethodContext(ContextPart)>handleSignal: 0x490d548: a(n) MethodContext 0xbff5ddec M MethodContext(ContextPart)>handleSignal: 0x490d5a8: a(n) MethodContext 0xbff5de10 M MethodContext(ContextPart)>handleSignal: 0x490d608: a(n) MethodContext 0xbff5de34 M MethodContext(ContextPart)>handleSignal: 0x490d668: a(n) MethodContext 0xbff5de58 M MethodContext(ContextPart)>handleSignal: 0x490d6c8: a(n) MethodContext 0xbff5de74 M ProgressInitiationException(Exception)>signal 0x1df4280: a(n) ProgressInitiationException 0xbff5de8c M ProgressInitiationException>display:at:from:to:during: 0x1df4280: a(n) ProgressInitiationException 0xbff5deb8 M ProgressInitiationException class>display:at:from:to:during: 0x2862fd8: a(n) ProgressInitiationException class 0xbff5dee4 M ByteString(String)>displayProgressAt:from:to:during: 0x1df3898: a(n) ByteString 0xbff5df0c M MetacelloSqueakPlatform>do:displaying: 0x4067c78: a(n) MetacelloSqueakPlatform 0xbff5df2c M MetacelloFetchingMCSpecLoader>linearLoadPackageSpec:gofer: 0x48ced80: a(n) MetacelloFetchingMCSpecLoader 0xbff5df4c M MetacelloPackageSpec>loadUsing:gofer: 0x48d11a0: a(n) MetacelloPackageSpec 0xbff5df70 M [] in MetacelloFetchingMCSpecLoader(MetacelloCommonMCSpecLoader)>linearLoadPackageSpecs:repositories: 0x48ced80: a(n) MetacelloFetchingMCSpecLoader 0xbff5df90 M OrderedCollection>do: 0x490d918: a(n) OrderedCollection 0xbff5dfb0 M MetacelloFetchingMCSpecLoader(MetacelloCommonMCSpecLoader)>linearLoadPackageSpecs:repositories: 0x48ced80: a(n) MetacelloFetchingMCSpecLoader 0xbff5dfe0 I [] in MetacelloFetchingMCSpecLoader>linearLoadPackageSpecs:repositories: 0x48ced80: a(n) MetacelloFetchingMCSpecLoader 0xbff5e000 M BlockClosure>ensure: 0x490d9a8: a(n) BlockClosure 0xbff5e028 I MetacelloLoaderPolicy>pushLoadDirective:during: 0x48b59c8: a(n) MetacelloLoaderPolicy 0x490da58 w MetacelloLoaderPolicy>pushLinearLoadDirectivesDuring:for: ```