Merge 10.8 into 10.9

Author: dr-m

storage/innobase/buf/buf0flu.cc

@@ -2432,7 +2432,6 @@ static void buf_flush_page_cleaner()
  break;
 
  const ulint dirty_blocks= UT_LIST_GET_LEN(buf_pool.flush_list);
- ut_ad(dirty_blocks);
  /* We perform dirty reads of the LRU+free list lengths here.
  Division by zero is not possible, because buf_pool.flush_list is
  guaranteed to be nonempty, and it is a subset of buf_pool.LRU. */