Crash when Building for iOS

I get the following error dialog popup when I Build & Run for iOS:

Unity 5.1.1f1 Personal

View attachment 145872

Exception Name: NSInvalidArgumentException
Description: -[NSURL length]: unrecognized selector sent to instance 0x13c0dab40
User Info: (null)

0 CoreFoundation 0x00007fff8c5c9735 __exceptionPreprocess + 165
1 libobjc.A.dylib 0x00007fff8e48b13a objc_exception_throw + 48
2 CoreFoundation...

Crash when Building for iOS