jsdialog: don't focus separators

Don't allow separator and spacer (placeolder which expands)
to be target of a focus when we use tab key.

Signed-off-by: Szymon Kłos <szymon.klos@collabora.com>
Change-Id: I724604eb299c65e4709d3e7708f514c312188393

browser/src/control/Control.JSDialogBuilder.js

@@ -3130,6 +3130,8 @@ L.Control.JSDialogBuilder = L.Control.extend({
 			&& data.type !== 'buttonbox'
 			&& data.type !== 'treelistbox'
 			&& data.type !== 'time'
+			&& data.type !== 'separator'
+			&& data.type !== 'spacer'
 			)
 			control.setAttribute('tabIndex', '0');
 	},