This handles it gracefully.
Given the kcm is usually in and will crash systemsettings i've a slight tendency towards this but would also be fine with an assert (or straight abort regardless of compile mode)

Ratio:
The code relies on the presence of an extern resource and produces "funny" crashes if absent - that somebody has to investigate.

I also propose to check kwin for similar hard deps on extern resources and handle them in a common way.

Yes, deleted main.qml -> crash.
W/ patch I get an ugly label telling me that i shall contact my distro because an important file is missing.