Add missing blank line after ListView class definition

Author: ctoth

gui_builder/forms.py

@@ -499,6 +499,7 @@ def set_item_column(self, index: int, column: int, data: Any):
         """Sets the string at the provided column and index to the provided value"""
         return self.widget.set_item_column(index, column, data)
 
+
 class ToolBar(UIForm):
     widget_type = widgets.ToolBar