URL.JS Fix causes an error in the console

[MaximSavin]

40601f8

This fix causes an error in the console:

Maxims-MacBook-Pro:bin maximsavin$ ./lessc style.less

/Users/maximsavin/Projects/less.js/lib/less/tree/url.js:8
        if (less.mode === 'browser' && !/^(?:https?:\/\/|file:\/\/|data:|\/)/.
                      ^
ReferenceError: less is not defined
    at Object.<anonymous> (/Users/maximsavin/Projects/less.js/lib/less/tree/url.js:8:23)
    at Object.<anonymous> (/Users/maximsavin/Projects/less.js/lib/less/parser.js:565:28)
    at $ (/Users/maximsavin/Projects/less.js/lib/less/parser.js:113:24)
    at Object.entity (/Users/maximsavin/Projects/less.js/lib/less/parser.js:768:81)
    at $ (/Users/maximsavin/Projects/less.js/lib/less/parser.js:113:24)
    at Object.expression (/Users/maximsavin/Projects/less.js/lib/less/parser.js:1097:48)
    at $ (/Users/maximsavin/Projects/less.js/lib/less/parser.js:113:24)
    at Object.value (/Users/maximsavin/Projects/less.js/lib/less/parser.js:1031:28)
    at $ (/Users/maximsavin/Projects/less.js/lib/less/parser.js:113:24)
    at Object.rule (/Users/maximsavin/Projects/less.js/lib/less/parser.js:944:33)

[andyfowler]

duplicate of #486

[MaximSavin]

oops sorry...