[System Tray] Fall back to tool tip title if no title is set

Some Electron apps send an empty tray icon title... Instead of showing an
awkward gap, use the tooltip title instead.


(cherry picked from commit 69f5c3a0)

applets/systemtray/package/contents/ui/items/StatusNotifierItem.qml

@@ -24,7 +24,7 @@ AbstractItem {
     id: taskIcon
 
     itemId: model.Id
-    text: model.Title
+    text: model.Title || model.ToolTipTitle
     mainText: model.ToolTipTitle !== "" ? model.ToolTipTitle : model.Title
     subText: model.ToolTipSubTitle
     textFormat: Text.AutoText