fix for "share" button on ipad iOS9+

[zkrige]

Crashes on ipad ios9+ if we dont set the UIPopoverPresentationController source

• (void)actionButtonClicked:(UIBarButtonItem *)sender {
  NSArray *activities = @[[SVWebViewControllerActivitySafari new], [SVWebViewControllerActivityChrome new]];

  UIActivityViewController *activityController = [[UIActivityViewController alloc] initWithActivityItems:@[self.self.webView.request.URL] applicationActivities:activities];
  if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad) {
  UIPopoverPresentationController *popPresenter = [activityController popoverPresentationController];
  popPresenter.barButtonItem = sender;

  }
  [self presentViewController:activityController animated:YES completion:nil];
  }