h264: Fix memory leak on ff_h264_decode_init() failure

CC: libav-devel@libav.org

libavcodec/h264.c

@@ -662,8 +662,10 @@ av_cold int ff_h264_decode_init(AVCodecContext *avctx)
 
     if (avctx->extradata_size > 0 && avctx->extradata) {
        ret = ff_h264_decode_extradata(h);
-       if (ret < 0)
+       if (ret < 0) {
+           ff_h264_free_context(h);
            return ret;
+       }
     }
 
     if (h->sps.bitstream_restriction_flag &&