When you activate Chrome Developers Tools with the "Pause on all exceptions" option, it constantly stops at this line:

PHP Code:
var cs root.querySelectorAll(path); 
ext-all.js (line 856)

the path variable holds " > div.x-date-mp". This selector syntax is not supported by chrome and causes this line to return "Error: SYNTAX_ERR: DOM Exception 12".

Because it's inside a try / catch it eventually recovers from the error but can we come up with a more elegant solution?