Cycling through Tri-state checkbox does not work if the first sub-clause has no child nodes

[NoahGresser]

In "Step 2: Refine clause selection", if a child node clause with no further children (such as "6.1 Audio bandwidth for speech" or "6.3 Caller ID") has its and only its checkbox is selected, the tri-state checkbox of its parent clause will not remember that the child node's checkbox was selected when trying to cycle to the mixed state, and will instead select all child node checkboxes.