Tests and fixes for double-enumeration on AddRange and adding of null to PopsicleList
diff --git a/src/ProtocolBuffers.Test/TestProtos/UnitTestMessageSetProtoFile.cs b/src/ProtocolBuffers.Test/TestProtos/UnitTestMessageSetProtoFile.cs
index 8a6bb58..34de1a9 100644
--- a/src/ProtocolBuffers.Test/TestProtos/UnitTestMessageSetProtoFile.cs
+++ b/src/ProtocolBuffers.Test/TestProtos/UnitTestMessageSetProtoFile.cs
@@ -1499,7 +1499,7 @@
       public override Builder MergeFrom(RawMessageSet other) {

         if (other == global::Google.ProtocolBuffers.TestProtos.RawMessageSet.DefaultInstance) return this;

         if (other.item_.Count != 0) {

-          base.AddRange(other.item_, result.item_);

+          result.item_.Add(other.item_);

         }

         this.MergeUnknownFields(other.UnknownFields);

         return this;

@@ -1587,7 +1587,7 @@
         return this;

       }

       public Builder AddRangeItem(scg::IEnumerable<global::Google.ProtocolBuffers.TestProtos.RawMessageSet.Types.Item> values) {

-        base.AddRange(values, result.item_);

+        result.item_.Add(values);

         return this;

       }

       public Builder ClearItem() {