Fix some nullable warnings (#4757)

Author: ekse

src/UniGetUI.Avalonia/Models/PackageCollections.cs

@@ -327,8 +327,8 @@ public IEnumerable<PackageWrapper> ApplyToList(IEnumerable<PackageWrapper> items
         Sorter.Checked => w.IsChecked ? "0" : "1",
         Sorter.Name => w.Package.Name,
         Sorter.Id => w.Package.Id,
-        Sorter.Version => w.Package.NormalizedVersion.ToString(),
-        Sorter.NewVersion => w.Package.NormalizedNewVersion.ToString(),
+        Sorter.Version => w.Package.NormalizedVersion.ToString() ?? string.Empty,
+        Sorter.NewVersion => w.Package.NormalizedNewVersion.ToString() ?? string.Empty,
         Sorter.Source => w.Package.Source.AsString_DisplayName,
         _ => w.Package.Name,
     };

src/UniGetUI.Avalonia/Views/Controls/Settings/CheckboxButtonCard.cs

@@ -94,7 +94,10 @@ public CheckboxButtonCard()
             StateChanged?.Invoke(this, EventArgs.Empty);
             Button.IsEnabled = (_checkbox.IsChecked ?? false) ? true : _buttonAlwaysOn;
             _textblock.Opacity = (_checkbox.IsChecked ?? false) ? 1 : 0.7;
-            AccessibilityAnnouncementService.AnnounceToggle(_textblock.Text, _checkbox.IsChecked ?? false);
+            if (_textblock.Text is not null)
+            {
+                AccessibilityAnnouncementService.AnnounceToggle(_textblock.Text, _checkbox.IsChecked ?? false);
+            }
         };
         Button.Click += (s, e) => Click?.Invoke(s, e);
         ApplyAutomationMetadata(_checkbox, _textblock.Text);

src/UniGetUI.Avalonia/Views/Controls/Settings/CheckboxCard.cs

@@ -118,7 +118,10 @@ protected virtual void _checkbox_Toggled(object? sender, RoutedEventArgs e)
         StateChanged?.Invoke(this, EventArgs.Empty);
         _textblock.Opacity = (_checkbox.IsChecked ?? false) ? 1 : 0.7;
         SyncToggleItemStatus();
-        AccessibilityAnnouncementService.AnnounceToggle(_textblock.Text, _checkbox.IsChecked ?? false);
+        if (_textblock.Text is not null)
+        {
+            AccessibilityAnnouncementService.AnnounceToggle(_textblock.Text, _checkbox.IsChecked ?? false);
+        }
         var cmd = StateChangedCommand;
         if (cmd?.CanExecute(null) == true)
             cmd.Execute(null);
@@ -133,9 +136,11 @@ protected void SyncToggleItemStatus()
         AutomationProperties.SetItemStatus(_checkbox, state);
         // Name with state suffix: guarantees VoiceOver announces state on macOS
         // where ToggleSwitch AX role may not expose IsChecked natively
-        string baseName = _textblock.Text;
+        string? baseName = _textblock.Text;
         if (!string.IsNullOrEmpty(baseName))
+        {
             AutomationProperties.SetName(_checkbox, $"{baseName}, {state}");
+        }
     }
 }
 
@@ -197,6 +202,9 @@ protected override void _checkbox_Toggled(object? sender, RoutedEventArgs e)
         StateChanged?.Invoke(this, EventArgs.Empty);
         _textblock.Opacity = (_checkbox.IsChecked ?? false) ? 1 : 0.7;
         SyncToggleItemStatus();
-        AccessibilityAnnouncementService.AnnounceToggle(_textblock.Text, _checkbox.IsChecked ?? false);
+        if (_textblock.Text is not null)
+        {
+            AccessibilityAnnouncementService.AnnounceToggle(_textblock.Text, _checkbox.IsChecked ?? false);
+        }
     }
 }

src/UniGetUI.Avalonia/Views/Controls/Settings/SecureCheckboxCard.cs

@@ -150,7 +150,10 @@ await SecureSettings.TrySet(
                 cmd.Execute(null);
             _textblock.Opacity = (_checkbox.IsChecked ?? false) ? 1 : 0.7;
             _checkbox.IsChecked = SecureSettings.Get(setting_name) ^ IS_INVERTED ^ ForceInversion;
-            AccessibilityAnnouncementService.AnnounceToggle(_textblock.Text, _checkbox.IsChecked ?? false);
+            if (_textblock.Text is not null)
+            {
+                AccessibilityAnnouncementService.AnnounceToggle(_textblock.Text, _checkbox.IsChecked ?? false);
+            }
             _loading.IsVisible = false;
             _checkbox.IsEnabled = true;
         }