Issue Summary

When adding external gadget "Quick Links" from Jira 8.22.0 in Confluence - it is showing blank rectangle

When same Confluence instance is connected to Jira 8.20.6, gadget is working as expected

(tested with Confluence 7.15.0)

This is reproducible on Data Center: (yes) 

Steps to Reproduce

1. Install Jira 8.22.0
2. Install Confluence 7.15.0
3. Setup External Gadgets in Confluence by adding Gadget Feed URL to Jira 8.22.0
4. Create new page in Confluence, click +>Other Macro>Quick Links.Add gadget and click Update

Expected Results

Gadget should be showing Jira links: 

Actual Results

Gadget is showing an empty rectangle:

Workaround

1. Stop jira
2. Move <JIRA_INSTALL>/atlassian-jira/WEB-INF/atlassian-bundled-plugins/jira-gadgets-plugin-8.22.0.jar to another (backup) directory
3. Download and copy jira-gadgets-plugin-8.20.6.jar into <JIRA_INSTALL>/atlassian-jira/WEB-INF/atlassian-bundled-plugins/
4. Start Jira

 It's not clear what is the other potential impact of this WA