Swift Streams SIGABRT error

I followed the Real-Time Communication with Streams Tutorial by luke_parham, and it runs well most of the time, but i occasionally get a SIGABRT crash in the line readAvailableBytes(stream: aStream as! InputStream). i cannot determine the cause of this. it happens randomly. any suggestions on how to resolve this would be appreciated.

@luke_parham Could you please help with this when you get a chance? Thank you - much appreciated! :]

Hey @luke_parham, can you please look at this issue? it continues to appear randomly.