This is great, Dallan! Huge improvement. I was working on my tree yesterday, and at one point I refreshed the sources list and saw that all the blank rows were gone, and I thought “Wow, look at that, he solved it!”
The one unanticipated side effect in my sources is pictured here:

The good news is that many of those “Media:” items were unattached to any evidences, so I could delete them. That still leaves me with quite a few of them, but at least I can see what evidences they’re attached to.
For example, I opened that first one, “Media: database and images REGI: 1880 U.S. census PLAC: Washington County, Indiana…” It was attached to an 1880 census event for a family of my relatives in that county, and on their profile pages the event source showed up as “Supporting Evidence.” The correctly formatted source for them was also in my sources, though, so it wasn’t too hard to assign that to the event, delete the “Supporting Evidence” source, and then go back and delete the corresponding “Media:” item out of my sources.
So I guess those “Media:” source items are garbled reiterations of other properly-formatted sources in my database? Not sure if this is an issue needing an urgent fix, since the overall issue has been effectively addressed. Assuming these garbled sources aren’t something you could just eliminate with a few keystrokes, I’m okay with fixing them one by one myself, since Rootsfinder has more important development issues to be worked on.