Merge commit '3b69f245dbe6e2016659a45c4bfe284f6c5ac57e' into release/2.4

* commit '3b69f245dbe6e2016659a45c4bfe284f6c5ac57e':
  h264: Make sure reinit failures mark the context as not initialized

Conflicts:
	libavcodec/h264_slice.c

See: e8714f6f93
Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/h264_slice.c

@@ -1475,6 +1475,7 @@ int ff_h264_decode_slice_header(H264Context *h, H264Context *h0)
 
     if (h->context_initialized &&
         (must_reinit || needs_reinit)) {
+        h->context_initialized = 0;
         if (h != h0) {
             av_log(h->avctx, AV_LOG_ERROR,
                    "changing width %d -> %d / height %d -> %d on "