Fix settings getting reset

fixes bugzid:531
	When a setting handle was created but never initialized/used, it
would override the current value with the default value on destruction.

libraries/shared/src/SettingInterface.cpp

@@ -97,7 +97,7 @@ namespace Setting {
     }
 
     void Interface::deinit() {
-        if (privateInstance) {
+        if (_isInitialized && privateInstance) {
             // Save value to disk
             save();