SettingsCell: Fix crash on iPad

This merge request fixes a crash issue on iPad when triggering the information button in the Settings View.

UIAlertController with UIModalPresentationPopover as a style need to set up the popoverPresentationController's sourceView & sourceRect.

By doing so, we specify the anchor location for the popover and therefore avoid any crash issue.

This merge request also removes a warning related to a variable that was declared but never mutated.

Alert on iPhone

Alert on iPad

Closes #1495 (closed)