Check_MK Werk 4381: Fixed exception when WATO ruleset without main group definition exists

ID: 4381 Title: Fixed exception when WATO ruleset without main group definition exists Component: WATO Level: 1 Class: Bug Fix Version: 1.5.0i1 An exception "AttributeError ('NoneType' object has no attribute 'title')" could occur on WATO ruleset list pages when a custom Check_MK ruleset definition exists without previous register_rulegroup() call for the main group.