Bookmark folder disappears after drag and drop in about:bookmarks

[bsclifton]

Did you search for similar issues before submitting this one?
Yes

Describe the issue you encountered:
I was drag and dropping in the new about:bookmarks screen and one of my folder disappeared. No matter what I did, I could not find the folder. The bookmarks are still there; you can search and find them. I opened the session file up and saw the the folder in question had it's parentFolderId set to the same number as the folderId (which should be impossible)

JSON from the session:

{
  "lastAccessedTime": 1475044276843,
  "tags": [
    "bookmark-folder"
  ],
  "folderId": 1,
  "customTitle": "favorites",
  "parentFolderId": 1
},

Expected behavior:
You should never be able to move a folder onto itself

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Mac, but @alexwykoff had it occur on Windows
• Brave Version:
  HEAD of master
• Steps to reproduce:
  I cannot reliably reproduce, but @alexwykoff had encountered the issue too
• Screenshot if needed:
  
• Any related issues: