Issue when creating variables with incorrect names.

[fviale]

Issue appear when creating a variable with an incorrect name and a Model is defined.

First step (which is ok), an error message appears:

When trying to fix the variable name, the error message does not disappear:

After cancelling the form and reloading, several variables appear in the list instead of one:

[amouhoub]

@fviale is this fixed by the aforementioned commits of yours ?