It's a quality container, not a material container. This was a copy-paste mistake.
Also added that this may be a global quality container, not always a per-extruder quality container.
Found during testing & tooling.
Previously it would use the material type from the material, but since
the material from the node can be different to that of the quality, we need
to use the one from quality instead (This is due to the fallback system)
CURA-6807
You can now be assured that there is ALWAYS at least one child node, except for child nodes of intent profiles which don't exist.
Contributes to issue CURA-6600.
Among the machines, variants, materials, qualities and intents, only machines and materials can ever be added during runtime. For the rest, we don't need to listen to these signals.
Contributes to issue CURA-6600.
