avcodec/g2meet: Also clear tile dimensions on header_fail

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit fb04666995)

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/g2meet.c

@@ -877,6 +877,8 @@ header_fail:
     c->height  = 0;
     c->tiles_x =
     c->tiles_y = 0;
+    c->tile_width =
+    c->tile_height = 0;
     return ret;
 }