avcodec/v4l2_m2m: Check if the file descriptor is valid before closing

Fixes ticket #9507.

Reviewed-by: Steven Liu <liuqi05@kuaishou.com>
Signed-off-by: wujian_nanjing <wujian2@huawei.com>

libavcodec/v4l2_m2m.c

@@ -251,6 +251,7 @@ static void v4l2_m2m_destroy_context(void *opaque, uint8_t *context)
     ff_v4l2_context_release(&s->capture);
     sem_destroy(&s->refsync);
 
+    if (s->fd >= 0)
         close(s->fd);
     av_frame_unref(s->frame);
     av_frame_free(&s->frame);