There is a php warning that we're seeing for missing #type in $variables for the widget form element. In this case it's showing up in the themable_forms module and a custom theme that we have, but it's probably likely to show up in other places as I believe having a #type is assumed.
It'd probably be good practice to add #type => container to the widget, I've seen it in the AddressDefaultWidget in the address module for example, which has a similar structure.
I've tested it out on our end and it doesn't seem to change any of the functionality.
Needs review
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