Merge pull request #1780 from tmeschter/Fix1596

Set correct checkmarks in "Set Rule Set Severity"

src/VisualStudio/Core/SolutionExplorerShim/AnalyzersCommandHandler.cs

@@ -267,11 +267,15 @@ private void UpdateSeverityMenuItemsChecked()
                     foreach (var diagnosticItem in group)
                     {
                         ReportDiagnostic ruleSetSeverity;
-                        if (specificOptions.TryGetValue(diagnosticItem.Descriptor.Id, out ruleSetSeverity) &&
-                            ruleSetSeverity != ReportDiagnostic.Default)
+                        if (specificOptions.TryGetValue(diagnosticItem.Descriptor.Id, out ruleSetSeverity))
                         {
                             selectedItemSeverities.Add(ruleSetSeverity);
                         }
+                        else
+                        {
+                            // The rule has no setting.
+                            selectedItemSeverities.Add(ReportDiagnostic.Default);
+                        }
                     }
                 }
             }