Blank screen seen after clicking Authorize on Authorization Request portlet

Steps to reproduce:

1. Add a new OAuth 2 application 
2. Navigate to the authorization code endpoint for the created application
3. Click the Authorize or Cancel button

Expected result:
Expected no warnings in the console and to be re-directed to the home page with the authorization code seen in the URL

Actual Result:
A blank page is seen.

Following warning seen in console:

javax.ws.rs.ClientErrorException: HTTP 415 Unsupported Media Type  

Full console logs here

Reproduced on:
Tomcat 9.0.10 + MySQL 5.7.25
Portal master GIT ID: 5031d8ccf3ba2c39134c60abc6c2cea84d6c3f66