Null check the R classes from config in TrackResourcesPass
Null check the R classes from config in TrackResourcesPass

Summary: Make this a little more resilient for the case where a config is used across many apps, of which different types of resources may not exist.

Reviewed By: kuganv

Differential Revision: D32379145

fbshipit-source-id: a87cf7a238b5f4aff9b4f254017cc06c97f17774

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex