Bug Description

When in Firefox, flipping a background image causes a weird redirect.

Reported by Claudio in #578 (Firefox 74)

Expected Behaviour

Steps to Reproduce

1. opted to create New story
2. selected an image
3. selected "Set As Backgrpound"
4. in right panel, selected option to flip (top arrow):
   
5. image flipped but I'm automatically redirected to Add Post:
   

Note: The above steps are from Claudio. When I (Jason) tested, I get redirected to the All Posts list in the WP admin.

Screenshots

Do not alter or remove anything below. The following sections will be managed by moderators only.

Acceptance Criteria

QA Instructions