Fixed warnings that come up when opening AppStore link
Fixed warnings that come up when opening AppStore link

Pressing the 'Update' button that opens up AppStore shows these warnings:

```
_BSMachError: (os/kern) invalid capability (20)
_BSMachError: (os/kern) invalid name (15)
```

This simple fix makes sure alert action is handled on main thread which in return doesn't show any warnings. Relevant stackoverflow answer: http://stackoverflow.com/a/33639650/2734193
ArtSabintsev/Harpy