When language is changed, admin status is removed

Hy, During a quick check, I recognize this line is the problem:
https://code.vtiger.com/vtiger/vtigercrm/blob/master/modules/Users/actions/SaveAjax.php#L106

Reason is, during SaveAjax, the is_admin fieldvalue is never "on". I suppose this is a stronger permission handling, but the fieldvalue should only updated, when field also is transfered.

I will prepare a Merge Request to get a solution.