Fix: Dispose stream and clear document on RichTextPreview unload

src/Files.App/UserControls/FilePreviews/RichTextPreview.xaml

@@ -8,6 +8,7 @@
 	xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
 	d:DesignHeight="300"
 	d:DesignWidth="400"
+	Unloaded="RichTextPreview_Unloaded"
 	mc:Ignorable="d">
 
 	<Border>

src/Files.App/UserControls/FilePreviews/RichTextPreview.xaml.cs

@@ -17,7 +17,20 @@ public RichTextPreview(RichTextPreviewViewModel viewModel)
 
 		private void TextPreviewControl_Loaded(object sender, Microsoft.UI.Xaml.RoutedEventArgs e)
 		{
-			TextPreviewControl.Document.LoadFromStream(Microsoft.UI.Text.TextSetOptions.FormatRtf, ViewModel.Stream);
+			// Defensive check to prevent loading if stream is null or disposed
+			if (ViewModel.Stream is not null)
+			{
+				TextPreviewControl.Document.LoadFromStream(Microsoft.UI.Text.TextSetOptions.FormatRtf, ViewModel.Stream);
+			}
+		}
+
+		private void RichTextPreview_Unloaded(object sender, Microsoft.UI.Xaml.RoutedEventArgs e)
+		{
+			// Clear the document to release resources
+			TextPreviewControl.Document.SetText(Microsoft.UI.Text.TextSetOptions.None, string.Empty);
+
+			// Call the ViewModel's unload handler to dispose the stream
+			ViewModel.PreviewControlBase_Unloaded(sender, e);
 		}
 	}
 }

src/Files.App/ViewModels/UserControls/Previews/RichTextPreviewViewModel.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT License.
 
 using Files.App.ViewModels.Properties;
+using Microsoft.UI.Xaml;
 using Windows.Storage.Streams;
 
 namespace Files.App.ViewModels.Previews
@@ -21,5 +22,13 @@ public async override Task<List<FileProperty>> LoadPreviewAndDetailsAsync()
 
 			return [];
 		}
+
+		public override void PreviewControlBase_Unloaded(object sender, RoutedEventArgs e)
+		{
+			Stream?.Dispose();
+			Stream = null;
+
+			base.PreviewControlBase_Unloaded(sender, e);
+		}
 	}
 }