[pulse][objc][nil] Improve error message for nil insertion into collection and nil block call issues
[pulse][objc][nil] Improve error message for nil insertion into collection and nil block call issues

Reviewed By: skcho

Differential Revision: D29391031

fbshipit-source-id: 3113d7876

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