Crash at startup with: NSBigMutableString replaceCharactersInRange

Hey all, AudioFinder is repeatedly crashing out at startup with following error message (taken from log) anyone seen this before or can help to resolve? thank you!

*** Terminating app due to uncaught exception ‘NSInvalidArgumentException’, reason: ‘*** -[NSBigMutableString replaceCharactersInRange:withString:]: nil argument’
abort() called
terminating with uncaught exception of type NSException