Fixes #221 NetworkActivityIndicator not showing

[batjo]

When I change

if UIApplication.responds(to: NSSelectorFromString("shared")) {
    (UIApplication.value(forKeyPath: "shared") as? UIApplication)?.isNetworkActivityIndicatorVisible = (self.activitiesCount > 0)
}

To

if UIApplication.responds(to: NSSelectorFromString("sharedApplication")) {
    (UIApplication.value(forKeyPath: "sharedApplication") as? UIApplication)?.isNetworkActivityIndicatorVisible = (self.activitiesCount > 0)
}

it works. Not sure why since it's UIApplication.shared and not UIApplication.sharedApplication

[3lvis]

Thanks @batjo!