Bug(ConfigEditor): Do not reset the user password when validate changes

[a-lubert]

When the edit form is used in the users tab from the ConfigEditor, the password field will be empty (except if this field was altered in another edit, the cache is not reset).

But when the submit button is triggered, the user will be updated with the value of the password field. If the field was empty, the user will have an empty password.

The password do not needs to be updated if the field is empty (or filled from spaces) and the field must be reset, each time the form was opened.