avcodec/utils: Assert that the number of consumed bytes in avcodec_decode_audio4() is <= the input size

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

libavcodec/utils.c

@@ -2422,6 +2422,8 @@ fail:
             av_frame_unref(frame);
     }
 
+    av_assert0(ret <= avpkt->size);
+
     return ret;
 }