Custom rules crashing python backend

[bokov]

Probably need to go in via repl_python, grab a custom rule out of DFCol.chosen and see where it goes wrong. Similarly to #3. But not tonight.

[bokov]

Not all rules crash python. I tried with a custom one that covered all the custom UI elements (though the QB part was very simple) and it ran as intended.

Problem might be with specific rules.