10283: ICE in CTFE

Another fix required by my optimize(WANTinterpret) -> CTFE project.

Fixes a simple error-propagation bug relating to initializer errors in struct literals:

http://d.puremagic.com/issues/show_bug.cgi?id=10283

I also found a place where ctfeInterpret() wasn't being called. It's not really related to bug 10283, but both fixes are so trivial I've combined them here.