The original workaround was only supposed to apply to QList/
QVector of QVariantMaps. By replacing them all in sip we
break mapping of signals defined in c++ which are emitted
by Python code.
Fixes exceptions after running processing algorithms in Qt6
builds.
stored in a single place, and that we always use the default
value when its not overwise set
This has two benefits:
1. The user doesn't see confusing "0" values for radius/length etc,
which are silently treated as some other fixed value when rendering
2. The default values are correctly accounted for when calculating
the layer's AABB, otherwise we end up with a flat AABB by
default
