Clear out our projection buffers when we shutdown the preview window to workaround an editor bug.

Author: CyrusNajmabadi

src/EditorFeatures/Core/Implementation/Preview/PreviewFactoryService.cs

@@ -573,6 +573,15 @@ private async Task<object> CreateNewDifferenceViewerAsync(
 
             diffViewer.Closed += (s, e) =>
             {
+                // Workaround Editor bug.  The editor has an issue where they sometimes crash when 
+                // trying to apply changes to projection buffer.  So, when the user actually invokes
+                // a SuggestedAction we may then edit a text buffer, which the editor will then 
+                // try to propagate through the projections we have here over that buffer.  To ensure
+                // that that doesn't happen, we clear out the projections first so that this crash
+                // won't happen.
+                originalBuffer.DeleteSpans(0, originalBuffer.CurrentSnapshot.SpanCount);
+                changedBuffer.DeleteSpans(0, changedBuffer.CurrentSnapshot.SpanCount);
+
                 leftWorkspace?.Dispose();
                 leftWorkspace = null;