In the "Simple Filter Mode with Menu" example for filtering datagrids, you can apply filters to each column (pressing the "funnel" icon). For columns that are "string", one could use the "Is empty" criteria (which is different to the "is null" criteria, because a string can be empty or null). But since two or three versions back, the "is empty" criteria is missing from the filter context menu. Is that a bug? By design? It was very useful for us, because our data contained empty strings...
We will do our best to add it for our next update before the end of the week!