Preview Release 98 breaks menuloader

[theodox]

It looks like Preview Release 98 (= maya 2019 as of november 2018) breaks the menuLoader, because it does not coerce arguments to menu and menuItem to strings the way it used to. This will break the menuLoader because it currently relies on ,mGui objects looking like strings when appending or editing existing menus

We'll need to monitor this to make sure it is not a problem in release. I believe that this behavior was OK in preview releases 95 and 97 so it coould be transient

[theodox]

It's fixable if you add a string coercion inside get_insert_after_item but I think this extends to other gui commands as well, so we need to be careful