Set the minimum size for a listbox cell.

The images drawn for a selected cell require a minimum size.

The change is part 2/2 of the fix for bug #22144.

changelog

@@ -19,6 +19,7 @@ Version 1.11.15+dev:
    * Updated translations:
  * User interface:
    * Fixed bug #22095: An assertion failure in the gamestate inspector.
+   * Fixed bug #22144: An assertion failure with empty labels in a listbox.
  * WML engine:
    * Fixed a regression in 1.11.14 causing WML parser/preprocessor errors to
      not interrupt the game load sequence or display an error message in-game,

data/gui/default/widget/toggle_panel_default.cfg

@@ -20,8 +20,11 @@
 
 	[resolution]
 
+		# The minimum required height is due to the size required for
+		# {GUI__LISTBOX_SELECTED_CELL}
+		# The issue was found bug #22144
 		min_width = 0
-		min_height = 0
+		min_height = 26
 
 		default_width = 0
 		default_height = 0