don't convert undefined to null in rpc requests

lib/rpc.js

@@ -90,6 +90,10 @@ function serialize(realmId, value) {
         return {type: objectTypes.FUNCTION};
     }
 
+    if (typeof value === 'undefined') {
+        return {type: 'undefined'};
+    }
+
     if (!value || typeof value != 'object') {
         return {value: value};
     }

src/RealmRPC.cpp

@@ -315,6 +315,10 @@ JSValueRef RPCServer::deserialize_json_value(const json dict)
             }
             return date;
         }
+        else if (type_string == "undefined") {
+            return JSValueMakeUndefined(m_context);
+        }
+        assert(0);
     }
 
     if (value.is_null()) {
@@ -353,5 +357,5 @@ JSValueRef RPCServer::deserialize_json_value(const json dict)
         return js_object;
     }
 
-    return JSValueMakeUndefined(m_context);
+    assert(0);
 }