fix unused tag defaulting to 'Show Email'

as 'Show Email' has randomly the value 0,
which is the same iOS assignes by default,
tapping on some switch cells opens 'Show Email'.

we fix this by explicitly adding a defaultTagValue that is zero.

deltachat-ios/Controller/Settings/AdvancedViewController.swift

@@ -12,8 +12,8 @@ internal final class AdvancedViewController: UITableViewController, ProgressAler
     }
 
     private enum CellTags: Int {
+        case defaultTagValue = 0
         case showEmails
-        case autocryptPreferences
         case sendAutocryptMessage
         case manageKeys
         case videoChat
@@ -49,7 +49,6 @@ internal final class AdvancedViewController: UITableViewController, ProgressAler
 
     private lazy var autocryptPreferencesCell: UITableViewCell = {
         let cell = UITableViewCell(style: .default, reuseIdentifier: nil)
-        cell.tag = CellTags.autocryptPreferences.rawValue
         cell.textLabel?.text = String.localized("autocrypt_prefer_e2ee")
         cell.accessoryView = autocryptSwitch
         cell.selectionStyle = .none
@@ -307,12 +306,12 @@ internal final class AdvancedViewController: UITableViewController, ProgressAler
 
         switch cellTag {
         case .showEmails: showClassicMailController()
-        case .autocryptPreferences: break
         case .sendAutocryptMessage: sendAutocryptSetupMessage()
         case .manageKeys: showManageKeysDialog()
         case .videoChat: showVideoChatInstance()
         case .viewLog: showLogViewController()
         case .accountSettings: showAccountSettingsController()
+        case .defaultTagValue: break
         }
     }