For the `skirt_brim_extruder_nr` setting it is possible for the setting to be -1; this means that we have no preference for extruder. This allowed us to implement the "multi-material brim". When we were requesting the initial extruder, and this value was set to -1 we were default to the 0-th extruder. However, this was incorrect in the situation where the first extruder is not used.
Fixes#17501