Conflict between Cortex 1.7.4 and NYT's Emphasis

Emphasis: https://github.com/NYTimes/Emphasis
  announcement: http://open.blogs.nytimes.com/2011/01/11/emphasis-update-and-source/
  source: https://github.com/NYTimes/Emphasis/blob/master/js/emphasis-src.js
  location on nytimes.com: http://graphics8.nytimes.com/js/app/common/emphasis/app.js

Cortex: http://cortexapp.com/

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 The problem
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When Cortex is enabled in Chrome, you can't press shift twice to enable Emphasis.


 The problem in source
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Emphasis Line 56 errors and execution stops (see https://github.com/NYTimes/Emphasis/blob/master/js/emphasis-src.js#L56).

Manually running this line in the console produces this error:

> $$(".entry p:not(p[class]):not(:empty)", ".post p:not(p[class]):not(:empty)", "article p:not(p[class]):not(:empty)");
TypeError: Cannot call method 'match' of undefined

I've reduced this to this minimal test case:

> $$("*:empty")
TypeError: Cannot call method 'match' of undefined

When Cortex is disabled, Prototype returns full Element lists without error and Emphasis runs correctly.