Fix crash after import and restart

Fixes #23 and closes #27

Guard.Core/Storage/Database.cs

@@ -19,6 +19,9 @@ public static void Init()
             {
                 return;
             }
+            // Prevent empty strings from being converted to null
+            BsonMapper.Global.EmptyStringToNull = false;
+            // Initialize the database
             db = new LiteDatabase($"Filename={GetDBPath()}") { UserVersion = 1 };
 
             tokens = db.GetCollection<DBTOTPToken>("tokens");

Guard.WPF/Core/Icons/IconManager.cs

@@ -34,7 +34,7 @@ public static string[] GetIconNames()
 
         public static TotpIcon GetIcon(string name, IconType type)
         {
-            if (name == null || name == "default" || type == IconType.Default)
+            if (string.IsNullOrEmpty(name) || name == "default" || type == IconType.Default)
             {
                 return defaultIcon;
             }

Guard.WPF/Core/Import/Importer/AegisAuthenticatorImporter.cs

@@ -260,7 +260,7 @@ public bool RequiresPassword(string? path)
                     new()
                     {
                         Id = TokenManager.GetNextId(),
-                        Issuer = string.IsNullOrEmpty(token.Issuer) ? "???" : token.Issuer,
+                        Issuer = string.IsNullOrEmpty(token.Issuer) ? "" : token.Issuer,
                         EncryptedSecret = encryption.EncryptStringToBytes(normalizedSecret),
                         CreationTime = DateTime.Now
                     };
@@ -270,6 +270,11 @@ public bool RequiresPassword(string? path)
                     dbToken.EncryptedUsername = encryption.EncryptStringToBytes(token.Name);
                 }
 
+                if (string.IsNullOrEmpty(token.Issuer) && string.IsNullOrEmpty(token.Name))
+                {
+                    throw new Exception("Token must have either issuer or name set.");
+                }
+
                 if (icon != null && icon.Type != IconType.Default)
                 {
                     dbToken.Icon = icon.Name;

Guard.WPF/Core/Import/Importer/AuthenticatorProImporter.cs

@@ -76,7 +76,7 @@ private enum BackupType
             EncryptionHelper encryption = Auth.GetMainEncryptionHelper();
             foreach (var token in backup.Authenticators)
             {
-                if (token.Issuer == null)
+                if (string.IsNullOrEmpty(token.Issuer))
                 {
                     throw new Exception("Invalid AuthenticatorPro backup: No issuer found");
                 }

Guard.WPF/Core/Import/Importer/BitwardenImporter.cs

@@ -123,7 +123,7 @@ private static BitwardenEncryptionType GetEncryptionType(BitwardenExportFile exp
                 }
                 else
                 {
-                    if (item.Name == null)
+                    if (string.IsNullOrEmpty(item.Name))
                     {
                         throw new Exception("Invalid Bitwarden export file: No item name found");
                     }

Guard.WPF/Core/Import/OTPUriParser.cs

@@ -118,12 +118,12 @@ internal static OTPUri Parse(string uriString)
                 }
             }
 
-            if (otpUri.Issuer == null)
+            if (string.IsNullOrEmpty(otpUri.Issuer))
             {
                 throw new Exception($"Missing issuer in URI");
             }
 
-            if (otpUri.Secret == null)
+            if (string.IsNullOrEmpty(otpUri.Secret))
             {
                 throw new Exception($"Missing secret in URI from {otpUri.Issuer}");
             }

Guard.WPF/Views/Controls/TokenCard.xaml.cs

@@ -37,6 +37,11 @@ internal TokenCard(TOTPTokenHelper token)
 
             mainWindow = (MainWindow)Application.Current.MainWindow;
 
+            if (string.IsNullOrEmpty(token.dBToken.Issuer))
+            {
+                token.dBToken.Issuer = "???";
+            }
+
             Issuer.Text = token.dBToken.Issuer;
             if (token.dBToken.Issuer.Length > 18)
             {

Guard.WPF/Views/Pages/Add/TokenSettings.xaml.cs

@@ -66,6 +66,10 @@ public TokenSettings()
             // Set values if action is edit
             if (existingToken != null)
             {
+                if (string.IsNullOrEmpty(existingToken.dBToken.Issuer))
+                {
+                    existingToken.dBToken.Issuer = "???";
+                }
                 EncryptionHelper encryptionHelper = Auth.GetMainEncryptionHelper();
                 Issuer.Text = existingToken.dBToken.Issuer;
                 Secret.Password = encryptionHelper.DecryptBytesToString(