This compared to the other suggestions is cleaner and easier to understand
keeping the condition in the if() simple.

This affects alot of fate tests.

See: [FFmpeg-devel] [PATCH 05/11] avformat/nutenc: Don't pass NULL to memcmp
See: [FFmpeg-devel] [PATCH]lavf/nutenc: Do not call memcmp() with NULL argument

Fixes: Ticket 7980
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>