doc/examples/muxing: Use avio_closep() in examples as it avoids leaving stale pointers

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/examples/muxing.c

@@ -661,7 +661,7 @@ int main(int argc, char **argv)
 
     if (!(fmt->flags & AVFMT_NOFILE))
         /* Close the output file. */
-        avio_close(oc->pb);
+        avio_closep(&oc->pb);
 
     /* free the stream */
     avformat_free_context(oc);