safeguard against the lack of disclosure menu in a matrix field

[i-just]

Description

If a matrix field added to a field layout has a hidden label, then it won’t have a disclosure menu either, but some of our code assumed the disclosure menu is always there.

Steps to reproduce:

• clean 5.9.5 installation with one site
• create a matrix field with all default params and an entry type that can contain only title
• create a section with an entry type that contains this matrix field; double-click on the added matrix field and check the “Hide” checkbox for the field’s “Label” (apply and save all the way)
• create an entry in that section - you should see the errors in the console straight away

Related issues

#18366