fix possible segfault

Origin commit data
------------------
Commit: f2c20866af
Author: TangoCash <eric@loxat.de>
Date: 2018-09-01 (Sat, 01 Sep 2018)

src/gui/personalize.cpp

@@ -986,6 +986,7 @@ void CPersonalizeGui::addPersonalizedItems()
 					}
  				}
 
+				if (fw)
 					delete fw;
 			}
 			else //handle and add separator as non personalized item and don't allow to add a separator as next but allow back button as next