#40779 will be caused if (1) having nested where condition for through
association, and (2) through scope has references values, and (3) the
model has no association which is the same name with table name.

In that case, the join root will be found by the table name but the join
root isn't related with association reflection.

This changes to return the table klass from join dependency tree, it
works regardless of whether the join root or join association children.

Fixes #40779.