The fix is likely not what was intended by the author of the offending code (and does not seem to be functional), but at least it fixes the hard crash outlined in CURA-1666
The result of the function was None, but I don't need None to be called whenever extruders changed. I need the function itself to be called.
Contributes to issues CURA-1278 and CURA-351.
Hasn't been tested much because there is no display for this in the front-end yet. It needs a setting data type to go with in order to display it. This model is for the drop-down boxes to select an extruder to print, for instance, the support with.
Contributes to issues CURA-1278 and CURA-351.
