Merge pull request #38112 from chborl/fix38111

Fix null reference error when opening a miscellaneous files file

src/EditorFeatures/Core/Implementation/MetadataAsSource/MetadataAsSourceFileService.cs

@@ -224,10 +224,9 @@ public bool TryAddDocumentToWorkspace(string filePath, ITextBuffer buffer)
         {
             using (_gate.DisposableWait())
             {
-                Contract.ThrowIfNull(_workspace);
-
                 if (_generatedFilenameToInformation.TryGetValue(filePath, out var fileInfo))
                 {
+                    Contract.ThrowIfNull(_workspace);
                     Contract.ThrowIfTrue(_openedDocumentIds.ContainsKey(fileInfo));
 
                     // We do own the file, so let's open it up in our workspace