Parser: exit out more quickly on errors
Parser: exit out more quickly on errors

Fixes some crashes on things like unterminated strings.

mmp/pbrt-v3,mmp/pbrt-v3,mmp/pbrt-v3,mmp/pbrt-v3,nyue/pbrt-v3,nyue/pbrt-v3,nyue/pbrt-v3,nyue/pbrt-v3