Creating a mini layout with the same name as an existing layout creates errors

[argiepiano]

Steps to reproduce

1. Create a normal layout with machine name 'test'. Add some context and other stuff like blocks
2. Create a mini layout and use 'test' in the Admin label. Save it.

You get:

and the mini layout shows the context and other stuff from the normal layout itself:

Trying to delete it you get:

And then a fatal error:

[argiepiano]

This should have the same behavior as a normal layout when you try to use an existing machine name: