[EnterMode = BR] JS error when trying to create a list

[Wiktor Walc]

Found in FF13, there is a different error in IE9 in the same line.

1. Load _samples/enterkey.html
2. Switch to enter mode = BR
3. Move cursor at the end of first line
4. Press enter to create new line
5. Click List button

Result in Firefox:

sibling.is is not a function

if ( sibling && sibling.is( listNode.getName() ) )

list/plugin.js, line 703

Result in IE9:

Object doesn't support property or method 'is' 

list/plugin.js, line 703 character 4

Introduced in [7540]