lavu/fifo: fix regression

offset_w might be updated after growing the FIFO

Fix ticket #9630

Tested-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
Reviewed-by: mkver
Reviewed-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>

libavutil/fifo.c

@@ -147,13 +147,15 @@ static int fifo_write_common(AVFifo *f, const uint8_t *buf, size_t *nb_elems,
                              AVFifoCB read_cb, void *opaque)
 {
     size_t to_write = *nb_elems;
-    size_t offset_w = f->offset_w;
+    size_t offset_w;
     int         ret = 0;
 
     ret = fifo_check_space(f, to_write);
     if (ret < 0)
         return ret;
 
+    offset_w = f->offset_w;
+
     while (to_write > 0) {
         size_t    len = FFMIN(f->nb_elems - offset_w, to_write);
         uint8_t *wptr = f->buffer + offset_w * f->elem_size;