[12.0] muk_dms: Error when searching on root folder in Documents view

[mkanderson]

Description: entering an arbitrary search string in the search field of the Documents view while a root directory is selected causes the following error:

`Error:
Uncaught TypeError: Cannot read property 'odoo_id' of undefined

https://demo12.mukit.at/web/content/1015-ba35e8a/web.assets_backend.js:4234
Traceback:
TypeError: Cannot read property 'odoo_id' of undefined
at Class._searchNodes (https://demo12.mukit.at/web/content/1015-ba35e8a/web.assets_backend.js:4234:372)
at Class.search (https://demo12.mukit.at/web/content/1015-ba35e8a/web.assets_backend.js:4229:216)
at Class._searchData (https://demo12.mukit.at/web/content/1015-ba35e8a/web.assets_backend.js:4219:413)
at $.jstree.plugins.contextmenu.search (https://demo12.mukit.at/muk_dms_view/static/lib/jsTree/jstree.js:7531:15)
at Class.search (https://demo12.mukit.at/web/content/1015-ba35e8a/web.assets_backend.js:4211:3014)
at Class. (https://demo12.mukit.at/web/content/1015-ba35e8a/web.assets_backend.js:4254:346)
at later (https://demo12.mukit.at/web/content/1014-96363f7/web.assets_common.js:46:255)`

Reproducible at https://demo12.mukit.at/

• Navigate to "Documents" application, "Documents" menu, select a root folder "Documents Access Control" or "Documents Storage" and type anything the search bar.