This is a bugfix for #7195 (ThemeRoller Bookmarklet not working) – jQuery UI
To use it, put the contents of the patched bookmarklet in the bookmarklet instead of what you got from the original bookmarklet. To do this, right-click on the bookmarklet, select Properties, and replace the "Location" field with the contents of the patched bookmarklet link above.
Look at the git history of the gist history (not available in githubs user interface it seems) to see the diffs for the bookmarklet and developertool.js(.php?)
But basically I just implemented the patch referenced by the bug report and made it easy for others to use.
Beware, though, that apparently the source for ThemeRoller is currently not available. So a real upstream bugfix may not be easy.