Find first potential editorconfig when trying to synchronize (#74986)

Probably fixes a lot of reports of #54556

Author: Andrew Hall

src/VisualStudio/Core/Def/EditorConfigSettings/SettingsEditorControl.xaml.cs

@@ -82,7 +82,10 @@ internal void SynchronizeSettings()
 
         var solution = _workspace.CurrentSolution;
         var analyzerConfigDocument = solution.Projects
-            .Select(p => p.TryGetExistingAnalyzerConfigDocumentAtPath(_filepath)).FirstOrDefault();
+            .Select(p => p.TryGetExistingAnalyzerConfigDocumentAtPath(_filepath))
+            .WhereNotNull()
+            .FirstOrDefault();
+
         if (analyzerConfigDocument is null)
         {
             return;