fix add store credit icon button

preview

![screen shot 2013-11-21 at 10 53 05 am](https://f.cloud.github.com/assets/317648/1594803/6153a84e-52e0-11e3-8972-299d2fc8eb13.png)

before

![screen shot 2013-11-21 at 11 09 26 am](https://f.cloud.github.com/assets/317648/1594813/7f1fbff2-52e0-11e3-847b-36be0cb53b2f.png)