Fixed cell height when an empty string is given.

Signed-off-by: weisj <weisj@arcor.de>

core/src/main/java/com/github/weisj/darklaf/ui/list/DarkListCellRenderer.java

@@ -80,6 +80,10 @@ public class DarkListCellRenderer extends DefaultListCellRenderer {
                 comp.setForeground(UIManager.getColor("List.selectionForegroundInactive"));
             }
         }
+        if (getText().isEmpty()) {
+            //Fix cell height for empty string.
+            setText(" ");
+        }
         return comp;
     }
 }