Fixed a memleak in picture_fifo_Delete().

(cherry picked from commit 37bef1d6)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

src/misc/picture_fifo.c

@@ -146,5 +146,6 @@ void picture_fifo_Delete(picture_fifo_t *fifo)
 {
     picture_fifo_Flush(fifo, INT64_MAX, true);
     vlc_mutex_destroy(&fifo->lock);
+    free(fifo);
 }