Fix is similar to rac_get_model_sym()
Fixes: 1483/clusterfuzz-testcase-minimized-6386507814273024
Fixes: 1485/clusterfuzz-testcase-minimized-6639880215986176
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>