fix analysis error in fake

Author: jcollins-g

testing/test_package/lib/fake.dart

@@ -985,6 +985,8 @@ enum MacrosFromAccessors {
 /// Testing if docs for inherited method are correct.
 /// {@category NotSoExcellent}
 class SubForDocComments extends BaseForDocComments {
+  SubForDocComments(bool thing) : super(thing);
+  
   /// Reference to [foo] and [bar]
   void localMethod(String foo, bar) {}