Desktop: compact mode: Fix hidden button with undefined img

1. Load with notebookbar mode
2. Switch to compact mode via UI
3. Inspect -> see the existence of "#closemobile-button"
  - a div (unotoolbutton) with id closemobile that is hidden, has a
  button (unobutton) with id "closemobile-button" that is generated
  with an undefined img "lc_closemobile.svg" -> we don't have that

Add an alias. I don't think we ever use this. It seems to be a
temporary state that never gets to be shown to the user (is also
hidden) and when the UI is updated the HTML structure
changes. Nevertheless best to reference an image that exists

Signed-off-by: Pedro Pinto Silva <pedro.silva@collabora.com>
Change-Id: I500737d0e9a7c321f9f92e55c9348ca7064a6625

browser/src/control/Control.JSDialogBuilder.js

@@ -2097,6 +2097,9 @@ L.Control.JSDialogBuilder = L.Control.extend({
 		}
 
 		var iconURLAliases = {
+			// lc_closemobile.svg is generated when loading in NB mode then
+			// switch to compact mode: 1st hidden element in the top toolbar
+			'closemobile': 'closedocmobile',
 			'file-saveas': 'saveas',
 			'home-search': 'recsearch',
 			'addmb-menu': 'ok',