CComponentsTimer: exec OnTimer cleanup after stopped thread

Users reported about crashes, but I could not verify them by myself.

Supplement to: 8f7b23ad19


Origin commit data
------------------
Commit: 6e9e4de638
Author: Thilo Graf <dbt@novatux.de>
Date: 2017-05-29 (Mon, 29 May 2017)

src/gui/components/cc_timer.cpp

@@ -143,10 +143,12 @@ bool CComponentsTimer::startTimer()
 bool CComponentsTimer::stopTimer()
 {
 	tm_enable = false;
-	OnTimer.clear();
 	stopThread();
-	if(tm_thread == 0)
+	if(tm_thread == 0){
+		if (!OnTimer.empty())
+			OnTimer.clear();
 		return true;
+	}
 
 	return false;
 }