Remove null markers to avoid NullReferenceException

Author: andyleejordan

src/PowerShellEditorServices/Services/Analysis/AnalysisService.cs

@@ -384,8 +384,11 @@ internal async Task DelayThenInvokeDiagnosticsAsync(ScriptFile[] filesToAnalyze,
 
         private void PublishScriptDiagnostics(ScriptFile scriptFile) => PublishScriptDiagnostics(scriptFile, scriptFile.DiagnosticMarkers);
 
-        private void PublishScriptDiagnostics(ScriptFile scriptFile, IReadOnlyList<ScriptFileMarker> markers)
+        private void PublishScriptDiagnostics(ScriptFile scriptFile, List<ScriptFileMarker> markers)
         {
+            // NOTE: Sometimes we have null markers for reasons we don't yet know, but we need to
+            // remove them.
+            _ = markers.RemoveAll(m => m is null);
             Diagnostic[] diagnostics = new Diagnostic[markers.Count];
 
             CorrectionTableEntry fileCorrections = _mostRecentCorrectionsByFile.GetOrAdd(