Steps to Reproduce
This, in my case, caused the Raven applet to appear in the Firefox tab itself, independent of the the desktop environment (raven was still opened, taking up the space it did over Firefox whenever I opened in it).
Specs
Budgie-Desktop v.10.5-200
Firefox v.69.0.1-172
(Latest patches as of September 24, 2019)
This issue has been deemed by the developers to be an issue related to Budgie, our primary desktop environment. As Budgie is a distro-agnostic project, developed by Solus but leveraged by other operating systems and projects, we maintain a dedicated issue tracker for it. This issue tracker can be found at https://github.com/solus-project/budgie-desktop
We encourage you to search for your issue there and if your issue is not found, please create it. Bugs filed, tracked, and resolved there ensure the wider Budgie community can engage in a solution to your issue. Do note that we do not consider your issue "invalid" by virtue of being closed here, but rather are trying to maintain the distro-agnostic nature of Budgie as well as maintaining focus of Solus-specific issues on this tracker.