i tried your code on OF 0.8.4, OS X 10.10 and Xcode 6.4 and it works fine.
the same code on OF 0.9.0 does throw this error message. But i don't know why.
[09:51:59.845] FigLimitedDiskCacheProvider_CopyProperty signalled err=-12784 (kFigBaseObjectError_PropertyNotFound) (no such property) at /SourceCache/CoreMedia/CoreMedia-1562.240/Prototypes/FigByteStreamPrototypes/FigLimitedDiskCacheProvider.c line 947
2015-12-21 09:51:59.849 testVideo8[1830:112822] assetReader: error during initialisation: Operation Stopped
2015-12-21 09:51:59.849 testVideo8[1830:112822] problem with creating asset reader.