macosx: fix possible SPMediaKeyTap crash
Adding nil to an NSArray would make it raise an NSInvalidArgumentException which in turn leads to an abort in dispatch_once: https://github.com/apple-oss-distributions/libdispatch/blob/55c3a68e9ec47f1c1d5bb9909404ce5f0351edef/src/object.m#L557
Fix #27487 (closed)