Bug: Unsafe DB connections and missing returns in cobol_refractor_controller.py #292

Description
In cobol_refractor_controller.py, the IRStateManager contains paths where a database connection (Connection | None) is used without a None-check before calling .cursor() or .commit(). Additionally, get_dead_paras and get_orphaned_vars lack fallback return statements if the manager ends up in an unhandled mode.

Impact
If the database connection fails or drops, the missing None-checks will cause a hard crash. The missing fallback returns violate type safety and risk returning None instead of the expected set, cascading into downstream errors.

Proposed Fix

• Add explicit self.conn is not None checks before executing SQLite operations.
• Add return set() as the default fallback for getter methods.
• Add regression tests to simulate dropped connections and invalid modes.