The boolean "isdisabled" of the SystemUser Entity is null and I can't change it back

Hello,

I have tried to change with Javascript console the value of the field "isdisabled" of the SystemUser Entity, but I got an error and it has set the value of the field to null.

When I try to change it back with Javascript, C# or anything else, I get an "Unexpected Error" (object reference not set to an instance of an object).

I have also tried to remove the user licence and put it back, but the value is still null.

I'm stuck with this...

Have you any idea ?

Thanks