fix `dynamic` type literal

lib/src/codegen/js_module_item_order.dart

Index: lib/src/codegen/js_module_item_order.dart
diff --git a/lib/src/codegen/js_module_item_order.dart b/lib/src/codegen/js_module_item_order.dart
index 378f6cfef0020e7f67073adf1651fb3c23ae412d..ae3ec003b6774bb226b9117658b69a6fdafe1734 100644
--- a/lib/src/codegen/js_module_item_order.dart
+++ b/lib/src/codegen/js_module_item_order.dart
@@ -180,6 +180,9 @@ class ModuleItemLoadOrder {
   bool libraryIsLoaded(LibraryElement library) {
     assert(library != _currentLibrary);
 
+    // DynamicElementImpl has no library.
+    if (library == null) return true;
+
     // The SDK is a special case: we optimize the order to prevent laziness.
     if (_isDartUri(library)) {
       // SDK is loaded before non-SDK libraries