Steps to reproduce:

• Create tags as admin User:

  Root
  └──  Tag 1
  └──  Tag 2
         └── Subtag 1
  

• remove "Taxonomy -> All functions" policy from Editor role
• add policies "Taxonomy->Read" and "Taxonomy->Assign"
• create "Editor" and login as "Editor"
• Try moving / deleting Subtag 1 using the tree's context Menu.

Result:
Action is not executed (expected) an empty alert is shown:

Expected:

• Alert should show a meaningful error message.
• Better: to be consistent with the content tree's context menu, options to move/delete should be disabled.