Custom iconset, empty first icon: console error
Hello. I think I found an issue. I am using a custom iconset with an empty first icon (empty string), as follows:

``` javascript
$('#mypicker').iconpicker({
    iconset: {
        iconClass: 'icomoon',
        iconClassFix: '',
        icons: [" ", "icon-youtube", "icon-linkedin", "icon-pinterest"],
    },
});
```

When I click the button to open the icon picker, the following shows up in the console:

```
Uncaught Error: Syntax error, unrecognized expression: i.    jquery-1.11.0.min.js:2
db.error              @ jquery-1.11.0.min.js:2
ob                    @ jquery-1.11.0.min.js:2
db                    @ jquery-1.11.0.min.js:2
n.fn.extend.find      @ jquery-1.11.0.min.js:2
Iconpicker.switchPage @ bootstrap-iconpicker.js:171
(anonymous function)  @ bootstrap-iconpicker.js:476
n.event.dispatch      @ jquery-1.11.0.min.js:3
r.handle              @ jquery-1.11.0.min.js:3
n.event.trigger       @ jquery-1.11.0.min.js:3
e.event.trigger       @ jquery-migrate-1.2.1.min.js:2
(anonymous function)  @ jquery-1.11.0.min.js:3
n.extend.each         @ jquery-1.11.0.min.js:2
n.fn.n.each           @ jquery-1.11.0.min.js:2
n.fn.extend.trigger   @ jquery-1.11.0.min.js:3
r                     @ bootstrap.min.js:6
b.show                @ bootstrap.min.js:6
(anonymous function)  @ bootstrap.min.js:6
n.extend.each         @ jquery-1.11.0.min.js:2
n.fn.n.each           @ jquery-1.11.0.min.js:2
a.fn.popover          @ bootstrap.min.js:6
(anonymous function)  @ bootstrap-iconpicker.js:480
n.event.dispatch      @ jquery-1.11.0.min.js:3
r.handle              @ jquery-1.11.0.min.js:3
```

Is there a proper way to add an empty icon? What am I doing wrong? I'm using version 1.7.0.
