only add ExtensionChildren to types with extension list

Author: mikeebowen

gen/DocumentFormat.OpenXml.Generator.Models/Generators/Elements/DataModelWriterExtensions.cs

@@ -320,15 +320,18 @@ static DocumentCommentOptions BuildTypeComments(OpenXmlGeneratorServices service
 
     private static void WriteMetadata(this IndentedTextWriter writer, OpenXmlGeneratorServices services, SchemaType containingType)
     {
-        writer.WriteLine("internal static List<string> ExtensionChildren = new List() {");
-
-        foreach (var child in containingType.ExtensionChildren)
+        if (containingType.KnownChildren is not null && containingType.KnownChildren.Any(c => c.QName.Name == "extLst") && containingType.ExtensionChildren is not null)
         {
-            writer.WriteLine($"\"{services.FindClassName(child.Name)}\",");
-        }
+            writer.WriteLine("internal static new List<string> ExtensionChildren = new List<string>() {");
 
-        writer.WriteLine("};");
-        writer.WriteLine();
+            foreach (var child in containingType.ExtensionChildren)
+            {
+                writer.WriteLine($"\"{services.FindClassName(child.Name)}\",");
+            }
+
+            writer.WriteLine("};");
+            writer.WriteLine();
+        }
 
         var attributes = containingType.Attributes;