This addon is obsolete with the current release-version of Grid.
This addon is a utility extension/plugin for Grid. The only thing it does is adding a right-click unit menu to your grid raid frames.
To make better use of this addon, I suggest using it with an addon like Clique to customize the mouse bindings.
Read this great post by trogdorhunter in the comments about how GridUnitMenu and Clique work together: Post
Set focus is a protected function, and when clicking this menu item, the addon will be blocked by blizzard code. However impractical this may be, there is no real way around that problem, so I have removed the "Set focus" entry from all dropdowns.
Reporting a bug
Please use the Curseforge ticket system to report bugs or problems. This gives me the option to reply to your reports and you can also easily attach files there if they are required. You can simply log in on Curseforge with your Curse or Wowace account.