CFStringGetCStringPtr() sometimes returns null - fix by using CFStringGetCString()

[ghost]

...verflow.com/questions/9166291/converting-a-cfstringref-to-char/9166500#9166500)

[arirusso]

@wmeissner Thanks, I'll test tonight

cc: @freepoulite

[adamjmurray]

+1

UniMIDI is causing Ruby to segfault in my project. I found this pull request and applied it to my local copy of ffi-coremidi, and it fixed the problem.

This also fixed someone's problem on stack overflow: http://stackoverflow.com/questions/14030213/ffi-null-pointer-error-with-unimidi

I can monkey patch ffi-coremidi in my project until this is released.

[arirusso]

@adamjmurray Lost track of this-- will merge later today. Thanks for the heads up!!