update_property with an unknown name silently does nothing

[petlenz]

update_property(material, property) with a pair that matches nothing returns without error:

auto* target = find_in_graph(material, property);
if (!target) return;          // core/property_engine.h:48

A typo in a driver therefore looks like a property that never changes.

Fix

Throw, naming the requested property and the material it was looked up on. wire_materials() already has a good diagnostic of this shape to copy.

All references are to main at 91bd26f.