The FontList.plist written by WebKit after <http://trac.webkit.org/changeset/48775> causes the Safari 4 to crash on launch (because it hands it off to CG which fails to populate its font database from it).
Created attachment 40164 [details]
Revert to saving the CG font DB property list at the root of FontList.plist
Fixed in <http://trac.webkit.org/projects/webkit/changeset/48787>.
If you have used any build between r48775 and r48787, you will need to delete
FontList.plist in order to not crash on launch.