h264: disable ER by default

The way it is currently designed is fundamentally unsafe and cannot be
reasonably fixed without completely rewriting it.

libavcodec/h264.h

@@ -727,6 +727,8 @@ typedef struct H264Context {
 
     int cur_chroma_format_idc;
 
+    int enable_er;
+
     AVBufferPool *qscale_table_pool;
     AVBufferPool *mb_type_pool;
     AVBufferPool *motion_val_pool;