misc: chore: Fix numerous NullReferenceExceptions, InvalidOperationExceptions

src/Ryujinx/UI/ViewModels/AppListFavoriteComparable.cs

@@ -37,7 +37,7 @@ namespace Ryujinx.Ava.UI.ViewModels
                 return app.Favorite ? -1 : 1;
             }
 
-            throw new InvalidCastException($"Cannot cast {o.GetType()} to {nameof(AppListFavoriteComparable)}");
+            throw new InvalidCastException($"Cannot cast {o?.GetType()} to {nameof(AppListFavoriteComparable)}");
         }
     }
 }

src/Ryujinx/UI/ViewModels/DownloadableContentManagerViewModel.cs

@@ -92,9 +92,9 @@ namespace Ryujinx.Ava.UI.ViewModels
 
             _applicationData = applicationData;
 
-            if (Application.Current.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
+            if (Application.Current?.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
             {
-                _storageProvider = desktop.MainWindow.StorageProvider;
+                _storageProvider = desktop.MainWindow?.StorageProvider;
             }
 
             LoadDownloadableContents();

src/Ryujinx/UI/ViewModels/Input/InputViewModel.cs

@@ -254,10 +254,13 @@ namespace Ryujinx.Ava.UI.ViewModels.Input
 
                 AvaloniaKeyboardDriver = new AvaloniaKeyboardDriver(owner);
 
-                _mainWindow.InputManager.GamepadDriver.OnGamepadConnected += HandleOnGamepadConnected;
-                _mainWindow.InputManager.GamepadDriver.OnGamepadDisconnected += HandleOnGamepadDisconnected;
+                if (_mainWindow != null)
+                {
+                    _mainWindow.InputManager.GamepadDriver.OnGamepadConnected += HandleOnGamepadConnected;
+                    _mainWindow.InputManager.GamepadDriver.OnGamepadDisconnected += HandleOnGamepadDisconnected;
 
-                _mainWindow.ViewModel.AppHost?.NpadManager.BlockInputUpdates();
+                    _mainWindow.ViewModel.AppHost?.NpadManager.BlockInputUpdates();
+                }
 
                 _isLoaded = false;
 
@@ -783,11 +786,14 @@ namespace Ryujinx.Ava.UI.ViewModels.Input
                         config = (ConfigViewModel as ControllerInputViewModel)?.Config.GetConfig();
                     }
 
-                    config.ControllerType = Controllers[_controller].Type;
+                    if (config != null)
+                    {
+                        config.ControllerType = Controllers[_controller].Type;
 
-                    string jsonString = JsonHelper.Serialize(config, _serializerContext.InputConfig);
+                        string jsonString = JsonHelper.Serialize(config, _serializerContext.InputConfig);
 
-                    await File.WriteAllTextAsync(path, jsonString);
+                        await File.WriteAllTextAsync(path, jsonString);
+                    }
 
                     LoadProfiles();
                 }

src/Ryujinx/UI/ViewModels/MainWindowViewModel.cs

@@ -1332,7 +1332,7 @@ namespace Ryujinx.Ava.UI.ViewModels
             }
             catch (MissingKeyException ex)
             {
-                if (Application.Current.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
+                if (Application.Current?.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
                 {
                     Logger.Error?.Print(LogClass.Application, ex.ToString());
 
@@ -1553,7 +1553,7 @@ namespace Ryujinx.Ava.UI.ViewModels
             {
                 Dispatcher.UIThread.InvokeAsync(() =>
                 {
-                    Application.Current.Styles.TryGetResource(args.VSyncMode,
+                    Application.Current!.Styles.TryGetResource(args.VSyncMode,
                         Application.Current.ActualThemeVariant,
                         out object color);
 

src/Ryujinx/UI/ViewModels/ModManagerViewModel.cs

@@ -279,7 +279,7 @@ namespace Ryujinx.Ava.UI.ViewModels
 
             foreach (var dir in directories)
             {
-                string dirToCreate = dir.Replace(directory.Parent.ToString(), destinationDir);
+                string dirToCreate = dir.Replace(directory.Parent?.ToString() ?? string.Empty, destinationDir);
 
                 // Mod already exists
                 if (Directory.Exists(dirToCreate))
@@ -302,7 +302,7 @@ namespace Ryujinx.Ava.UI.ViewModels
 
             foreach (var file in files)
             {
-                File.Copy(file, file.Replace(directory.Parent.ToString(), destinationDir), true);
+                File.Copy(file, file.Replace(directory.Parent?.ToString() ?? string.Empty, destinationDir), true);
             }
 
             LoadMods(_applicationId, _installedDlcIds);

src/Ryujinx/UI/ViewModels/TitleUpdateViewModel.cs

@@ -75,9 +75,9 @@ namespace Ryujinx.Ava.UI.ViewModels
 
             ApplicationData = applicationData;
 
-            if (Application.Current.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
+            if (Application.Current?.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
             {
-                StorageProvider = desktop.MainWindow.StorageProvider;
+                StorageProvider = desktop.MainWindow?.StorageProvider;
             }
 
             LoadUpdates();

src/Ryujinx/UI/ViewModels/XCITrimmerViewModel.cs

@@ -268,7 +268,11 @@ namespace Ryujinx.Ava.UI.ViewModels
                         result = String.Compare(x?.Name, y?.Name, StringComparison.Ordinal);
                         break;
                     case SortField.Saved:
-                        result = x.PotentialSavingsB.CompareTo(y.PotentialSavingsB);
+                        if (x != null && y != null)
+                        {
+                            result = x.PotentialSavingsB.CompareTo(y.PotentialSavingsB);
+                        }
+
                         break;
                 }