audiointerleave: deobfuscate a function call.

right above there is if (pkt) {<do stuff>; pkt = NULL}, so pkt is just a
fancy name for NULL at this point.

libavformat/audiointerleave.c

@@ -130,5 +130,5 @@ int ff_audio_rechunk_interleave(AVFormatContext *s, AVPacket *out, AVPacket *pkt
         }
     }
 
-    return get_packet(s, out, pkt, flush);
+    return get_packet(s, out, NULL, flush);
 }