Add test for not throwing on missing required

csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs

diff --git a/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs b/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs
index e1d4d78..704f2e5 100644
--- a/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs
+++ b/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs
@@ -262,6 +262,13 @@
         }

 

         [Test]

+        public void RequiredFieldsNoThrow()

+        {

+            TestRequired.Parser.ParseFrom(new byte[0]);

+            (TestRequired.Parser as MessageParser).ParseFrom(new byte[0]);

+        }

+

+        [Test]

         public void RequiredFieldsInExtensions()

         {

             var message = new TestAllExtensions();