The specification states "NSV files may contain a single file header. "
Fixes: out of array access
Fixes: nsv-asan-002f473f726a0dcbd3bd53e422c4fc40b3cf3421
Found-by: Paul Ch <paulcher@icloud.com>
Tested-by: Paul Ch <paulcher@icloud.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>