Customer scenario: Analyzer author writes a bolier plate analyzer that defines the rule that it intends to implement in future, but registers no analyzer actions for analysis. Adding such an analyzer to your analyzer assembly brings down the entire analysis, and no analyzers execute during command line build. The issue was reported for StyleCopAnalyzers package which has many such to-be-implemented analyzers.

Fixes #2980

Fix description: Add a null check around the place we compute set of all registered actions for analyzers.

Testing: Added regression tests + existing tests.