[Fuchs2468]

I've also found a way to hide empty widgets (adapted parts of code from Embuary Matrix skin), but, since I'm total newbie when it comes to Kodi, I'm not sure if it will work for all the widgets - I've just changed parts that affected widgets I'm using. If you're going to include these changes, they would need a thorough testing and, probably, they would need to be applied to other widget types as well. 

Code:

<visible>Integer.IsGreater(Container($PARAM[widgetid]).NumItems,0) | Container($PARAM[widgetid]).IsUpdating</visible>

Yes that is a good idea.
I had already thought about that, but it's all very time-consuming to test it in every possible skin view and widget setting.