avformat/mov: reuse existing err variable

Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/mov.c

@@ -5647,12 +5647,10 @@ static int mov_read_header(AVFormatContext *s)
             break;
         case AVMEDIA_TYPE_VIDEO:
             if (sc->display_matrix) {
-                int ret;
-
-                ret = av_stream_add_side_data(st, AV_PKT_DATA_DISPLAYMATRIX, (uint8_t*)sc->display_matrix,
+                err = av_stream_add_side_data(st, AV_PKT_DATA_DISPLAYMATRIX, (uint8_t*)sc->display_matrix,
                                               sizeof(int32_t) * 9);
-                if (ret < 0)
-                    return ret;
+                if (err < 0)
+                    return err;
 
                 sc->display_matrix = NULL;
             }