Concepts got lost after editing parents concpets

[DavidKi]

Steps to reproduce

1. Add a new concept in your projects concept tree
2. remove the link to the parent concept
3. try to link your concept to another parent concept

Expected behaviour

The added concept should be linked to the second parent

Actual behaviour

The system gives an error: "PUT Request api/v1/tree/concept/1595/broader/1593?t= failed with status 400. This concept does not exist"

So I guess after deleting the only parent, the child is not linked to anything and got lost. Probably it is still saved in the back-end (cannot check this due to access limitations) and one could recreate the linking there. But for front-end users a concept should appear as Top-Level-Concept after removing every parent and not got lost.
In Spacialist instead of the concepts name, now only the URL of the concept is displayed

[v1r0x]

Sorry for not answering for so long. When a concept is no longer linked to any parent, it gets deleted. In Spacialist you still see the URL, because in Spacialist concepts are linked by their URL and not their ID.
IMO there are several solutions for this problem:

1. Warn the user that removing the last parent will delete this concept (if it is not a top level concept as well)
2. Warn the user and let them decide what to do (same as right clicking on a concept and click on Delete concept)
3. Replace the x in the broader list with a ...-menu and let the user choose
4. Delete the concept (as it is now) and reset the view, so it is no longer possible to re-link that non-existing concept

I'd prefer option 1. or 2. (or 3. as it is similar to 2.). What is your prefered option from a user perspective?

[DavidKi]

Option 2 sounds good. Option 1 would be ok as well, but perhaps the user will quickly click the warning away, without fully understanding it. So, warning the user and wait for a response from the user sounds as a good solution for this.
Is it possible to give the user at this point the choice to make a concept to a top-level concept?