Refactor event handling and policy script error management

- Removed redundant log statement in HandleEvent for cleaner output.
- Enhanced policy script handling to check for script existence before execution, improving error handling and fallback logic.
- Updated error messages to provide clearer feedback when policy scripts are missing or fail to start.
- Bumped version to v0.21.2 to reflect these changes.

app/handle-event.go

@@ -37,7 +37,6 @@ func (l *Listener) HandleEvent(msg []byte) (err error) {
 		}
 	}()
 
-	log.I.F("HandleEvent: continuing with event processing...")
 	if len(msg) > 0 {
 		log.I.F("extra '%s'", msg)
 	}