Spectrum is an extension that allows developers to see what a website would look like with various colour vision deficiencies (an essential extension to anyone that needs to develop accessible applications).
Uncaught TypeError: e.className.match is not a function
The error is thrown from blanket.js line 23. I believe it has something to do with spectrum creating SVG elements, which aren't strings (rather an SVGAnimatedString).
I will raise the issue with Spectrum as well as they may be causing issues on other sites as well, but
isAuiLayer is still incorrect as it's called on every child in the document, and doesn't verify that those elements aren't SVGs. If bitbutcket ever had an SVG on the page for any reason this error would re-appear.
It's also worth making this dimming optional, such that an error in this function does not prevent the page from being used at all. It seems odd that since it can't dim the page I'm not able to merge pull requests as that's part of the core functionality of this tool.
EDIT: The bug for spectrum is here