Unable to create oAuth application link with non Atlassian applications.

Summary

Unable to create oAuth application link with non Atlassian applications.

Steps to Reproduce

1. Deploy a clean JIRA 7.7.x or 7.8.x instance;
2. Set the Base URL accordingly;
3. Go to the application link page and create an application link for a non-Atlassian application;
4. Once created, click on the Incoming/Outgoing authenticators options in order to configure the oAuth tokens;

Expected Results

• To be able to configure the oAuth settings properly without the missing Base URL alert (JIRA's base URL is set to undefinied but you are accessing JIRA from)
• The external app to connect to JIRA properly;

Actual Results

• The below alert related to the missing Base URL is thrown even if the Base URL is properly configured. If we click on the update the Base URL link and close the alert window, we're able to configure the oAuth settings, however, it does not work to connect from an external application.
  

Solution / Workaround

• Use JIRA 7.6.3 where the issue does not occur and the external application is able to connect to JIRA properly.