Fix missing calling of export helper function in decorated class-declaration (#8319)

src/compiler/transformers/ts.ts

@@ -2682,7 +2682,7 @@ namespace ts {
          */
         function isNamedExternalModuleExport(node: Node) {
             return isExternalModuleExport(node)
-                && hasModifier(node, ModifierFlags.Default);
+                && !hasModifier(node, ModifierFlags.Default);
         }
 
         /**