avformat: simplify avformat_close_input

avio_close checks by itself for NULL condition.

libavformat/utils.c

@@ -2709,7 +2709,7 @@ void avformat_close_input(AVFormatContext **ps)
         s->iformat->read_close(s);
     avformat_free_context(s);
     *ps = NULL;
-    if (pb)
+
     avio_close(pb);
 }