C#: add test case

Author: Jami Cogswell

csharp/ql/test/utils/model-generator/dataflow/NoSummaries.cs

@@ -131,4 +131,15 @@ public Dictionary<int, int> ReturnSimpleTypeDictionary(Dictionary<int, int> a)
     {
         return a;
     }
-}
+}
+
+// A neutral model should not be created for a parameterless constructor.
+public class ParameterlessConstructor
+{
+    public bool IsInitialized;
+
+    public ParameterlessConstructor()
+    {
+        IsInitialized = true;
+    }
+}