chore: add return False in check validation

Signed-off-by: behnazh-w <[email protected]>

src/macaron/slsa_analyzer/registry.py

@@ -152,6 +152,7 @@ def _validate_check(check: Any) -> bool:
                 "The registered Check %s is not a valid instance of BaseCheck.",
                 class_name,
             )
+            return False
 
         # Try to get the path to the check module file
         check_module = inspect.getmodule(check)