h264: Clear ERContext.cur_pic when unref'ing current picture.

Signed-off-by: Dale Curtis <dalecurtis@chromium.org>

libavcodec/h264.c

@@ -1972,6 +1972,10 @@ static int h264_frame_start(H264Context *h)
 
     h->cur_pic_ptr = pic;
     unref_picture(h, &h->cur_pic);
+    if (CONFIG_ERROR_RESILIENCE) {
+        h->er.cur_pic = NULL;
+    }
+
     if ((ret = ref_picture(h, &h->cur_pic, h->cur_pic_ptr)) < 0)
         return ret;