fix(templatetags): limit menu visibility + missing page id key = crash

[wesleyboar]

Overview

Fix that if any menu item does not have a reverse_id*†, then limit_visibility_in_menu.py will crash.

_{If a CMS page has no ID* set, it will still have a reverse_id, it's just blank. This fixes edge case of menu item not having the attr/key.†}

_{* I.e. an "ID" in Advanced Settings.
† E.g. CMS News category or article.}

Related

• copied from fix(templatetags): limit visibility + cms news = crash Core-CMS#571
• adds safety to test(apcd-cms): fp-1837 limit menu visibility by group #45

Changes

• check for reverse_id before using it

Testing

0. Load this branch on existing APCD setup.
1. Open any page of the site (not the CMS Administration).
2. Verify no crash (from newly introduced code).
3. Verify any of the test cases from #45 still work.

UI

N/A

[wesleyboar]

Merged based on its unobtrusive and safety, and it having been tested via Core in TACC/Core-CMS#571.