Redirect URI is mandatory even if only client credentials grant is selected

Problem/Motivation

The redirect URI is mandatory even though the "client credentials" grant does not require it.

If left empty you get:

Error message
1 error has been found:

Redirect URIs (value 1)

What's more:
A recent change seems to have hidden the input field if "Authorization code" is unchecked so it is even less obvious what is wrong.

FWIW: A current workaround:
Temporarily check "Authorization code", enter a dummy URI, uncheck "Authorization code" and proceed with the proper configuration.

Steps to reproduce

• Click "Add consumer" on the consumer list
• Configure a consumer for the "client credentials" grant, i.e. enter a label, a client ID, check only the "client credentials" grant type checkbox, enter a client secret and a user
• Hit save

Proposed resolution

The redirect URI should no longer be required if only the client credentials is checked.