Admin Authentication Sources pages show 500 error in some causes

[wxiaoguang]

If there is an error occurs during add(new) (eg: duplicated name), then 500 error occurs during template rendering:

* template: admin/auth/new:17:68: executing "admin/auth/new" at <.type.Int>: can't evaluate field Int in type interface {}
* template: admin/auth/source/oauth:5:93: executing "admin/auth/source/oauth" at <.oauth2_provider.Name>: can't evaluate field Name in type interface {}

If the admin uses a duplicated name on the edit page, there is another 500:

* Error 1062: Duplicate entry 'aa' for key 'login_source.UQE_login_source_name'

In a word, the login source page is too complex and there are many bugs for edge cases.

[Javonne-liu]

I also reported an error of 500. How is this problem solved?

[zeripath]

@Javonne-do please provide the issue number of that.