Fix crash when no world is selected and configure button is pressed.

by moving return statement out of if-then-else clause...

src/guiMainMenu.cpp

@@ -1048,8 +1048,8 @@ bool GUIMainMenu::OnEvent(const SEvent& event)
 					GUIConfigureWorld *menu = new GUIConfigureWorld(env, parent,
 										-1, menumgr, wspec);
 					menu->drop();
-					return true;
 				}
+				return true;
 			}
 			case GUI_ID_SERVERLIST_DELETE: {
 				gui::IGUIListBox *serverlist = (gui::IGUIListBox*)getElementFromId(GUI_ID_SERVERLIST);