codec: videotoolbox: handle kVTVideoDecoderReferenceMissingErr
The kVTVideoDecoderReferenceMissingErr error is not a critical one, but without it being handled here, it would lead to aborting with VideoToolbox and falling back to Software.
Reproduced this with a sample provided by zhilizhao(赵志立), related to !1790.
I assume that before this error code was introduced in macOS 12/iOS 15, VT did just return the NULL image buffer with a success status code, leading to the issue seen in !1790.