Fix CF bug arising from empty sequence
An empty sequence with ModeOR=True will return a decision of FALSE by default.
If this exists as the child of an AND sequence with ShortCircuit=True this can lead to a control flow bug, where this parent sequence both short-circuits, allowing PRGraph evaluation beyond it, and evaluation still continues within the sequence itself.
This MR adds a test for the bug, and fixes the problem. Described here #135