set command should give better errors.

[rec]

It should indicate:

1. a syntax error: set light.vis.ins..size = [9, 9]
2. if it's a missing or ambiguous variable, the first location where it goes off. set light.vis.size = [9, 9] should give an error like "No value "size" in light.visualizer: possible values are".

[rec]

Also: https://github.com/rec/echomesh/issues/426https://github.com/rec/echomesh/issues/426