[incr] Skip incremental invalidation when summary table is empty
[incr] Skip incremental invalidation when summary table is empty

Summary:
This is mostly to avoid logging lots of "invalidated 0 of 0 summaries"
nonsense, and shouldn't affect actual analysis behavior.

Reviewed By: jvillard

Differential Revision: D40986586

fbshipit-source-id: 0f2e95030ae825afbd6acfd5a860d663287f3f23

facebook/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer