"Data/Game Data" menu item causes crash

[RatcheT2497]

___________________________________________
############################################################################################
FATAL ERROR in
action number 1
of Draw Event
for object Camera:

DoConv :1: illegal undefined/null use
 at gml_Script_ui_init_game_data_activate (line 4) -     Camera.ui_game_data.active_type_guid = sorted[| ui_list_selection(Camera.ui_game_data.el_master)].GUID;
############################################################################################
--------------------------------------------------------------------------------------------
stack frame is
gml_Script_ui_init_game_data_activate (line 4)
called from - gml_Script_momu_editor_data (line 33) - ui_init_game_data_activate();
called from - gml_Script_menu_render_element (line 31) -         script_execute(argument0.onmouseup, argument0);
called from - gml_Script_menu_render (line 59) -             script_execute(thing.render, thing, mx1, my1, mx2, my2);
called from - gml_Script_menu_render_main (line 17) -         script_execute(thing.render, thing, xx + argument0.element_width * i, yy);
called from - gml_Script_draw_editor_menu (line 11) - script_execute(menu.render, menu, 0, yy);
called from - gml_Object_Camera_Draw_0 (line 11) -                 draw_editor_menu();

[DragoniteSpam]

I put this off for more than half a year and it ended up taking a grand total of less than an hour to deal with. There's a life lesson in there somewhere, probably.