LearnBoost/stylus — pull request #1778 by rakchaev (2014-12-08 14:02:12+00:00)
Title: Fix resolve-url for hash url

Doesn't work compiling with resolve-url flag for hash url:

```
$ cat ../hash.styl
// For IE8. Doesn't work hover on padding.
.my-class
background-image url('#')

$ bin/stylus --resolve-url ../hash.styl

/home/rakchaev/projects/stylus/bin/stylus:646
throw err;
^
TypeError: ../hash.styl:3:26
1| // For IE8. Doesn't work hover on padding.
2| .my-class
3|	background-image url('#')
-------------------------------^
4|

Cannot call method 'substr' of null
at ".my-class" (../hash.styl:2:1)
```