(This is the assert that was added in fix for MDEV-26047)

Table elimination may remove an ON expression from an outer join.
However SELECT_LEX::update_used_tables() will still call

  item->walk(&Item::eval_not_null_tables)

for eliminated expressions. If the subquery is constant and cheap
Item_cond_and will attempt to evaluate it, which will trigger an
assert.
The fix is not to call update_used_tables() or eval_not_null_tables()
for ON expressions that were eliminated.