Community Auth - User Levels

I have a pressing issue in which I have solved apart of it. 
My aim is to use Community Auth to verify and authenticate all my users based on specific roles, So far I have been able to implement a form in which users can register correctly, where an auth_level is assigned to them based on their selection of a rank name (administrator, supervisor, manager etc).
My problem is this: I have a section in which an administrator can create a rank, but when the rank is created the auth_level is 0, now that is not so much a problem as it can be made auto-incremental or a text input can allow them to define the auth level associated with the new rank. (any better suggestions on this part will be really appreciated)

The main problem is, once that rank has been created and assigned to a user who then logs in, this error comes up:

PHP Code:

A PHP Error was encountered Severity: Notice Message: Undefined offset: 0 


<- the number corresponds to the value of the auth_level of the rank. 
That is if it has not been configured here

PHP Code:

$config['levels_and_roles'] 


Is there a way to link my form with the config level part of the authentication? 
Any help will be appreciated.