Fixed bug where getActionBarHeight would throw a ResourcesNotFoundException

Fixed bug where ```getActionBarHeight``` would throw a ```ResourcesNotFoundException``` if custom value was set for ```android:actionBarSize``` in the theme.

To replicate bug, in the current app's theme set: 
```
<item name="android:actionBarSize">56dp</item>
```
Then constructing a new SystemBarTintManager will throw a ```Resources$NotFoundException```

It looks as is this bug may be related to issues seen by @nubela in issue #8

Cheers, Rich