PLF-2322: [Navigation Selector] Unknown Error when clicking the "arrow up"

Fix description:
	- Do not update anything if the destination node is null
PLF-5012: Info about exo:gadget-groovy annoies server log when starting package in debug mode

Fix description:
- Verify existence of script objects before fetching them
PLF-5115: Add keys for space's default applications.

Conflicts:
	samples/acme-intranet/webapp/src/main/resources/locale/portal/webui_en.properties