xvba-buffer.c: destroy_va_buffer: disable check for map refcount.

Disable the check for the mapping refcount in destroy_va_buffer() since
some ffmpeg version have a bug that they do not unmap the buffer properly
in certain error paths.

src/xvba_buffer.c

@@ -228,7 +228,7 @@ destroy_va_buffer(
     if (!obj_buffer)
         return;
 
-    ASSERT(obj_buffer->map_refcnt == 0);
+    //ASSERT(obj_buffer->map_refcnt == 0);
 
     if (obj_buffer->buffer_data) {
         free(obj_buffer->buffer_data);