Nothing happens after clicking "add an icon from grid > Font awesome"
Nothing happens after clicking "add an icon from grid > Font awesome".
Sketch v3.4.2 and latest FontAwesome .otf installed.

Error in console is:

```
Sketch[59992]: Exception: TypeError: 'undefined' is not a function (evaluating 'searchbox.setPlaceholderString_(  "Search an icon...")')

Font Awesome (Sketch Plugin)[59992]: TypeError: 'undefined' is not a function (evaluating 'searchbox.setPlaceholderString_(  "Search an icon...")')
line: 424
sourceURL: /Users/X/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Sketch Iconfont/iconfont.sketchplugin/Contents/Sketch/add_icon_grid.cocoascript
stack: onRun@/Users/X/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Sketch Iconfont/iconfont.sketchplugin/Contents/Sketch/add_icon_grid.cocoascript:424:34
onFontawesome@/Users/X/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Sketch Iconfont/iconfont.sketchplugin/Contents/Sketch/add_icon_grid.cocoascript:355:8
```
