avcodec/h261dec: Fix context initialization sequence

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/h261dec.c

@@ -609,11 +609,10 @@ retry:
         s->parse_context = pc;
     }
 
-    if (!s->context_initialized)
+    if (!s->context_initialized) {
         if ((ret = ff_MPV_common_init(s)) < 0)
             return ret;
 
-    if (!s->context_initialized) {
         ret = ff_set_dimensions(avctx, s->width, s->height);
         if (ret < 0)
             return ret;