Moved named class argument check error to a more sensible location and amended error message

lib/class.js

@@ -259,17 +259,17 @@ function createNamedClass( name, def )
         );
     }
 
-    // add the name to the definition
-    def.__name = name;
-
     // the definition must be an object
     if ( typeof def !== 'object' )
     {
         throw TypeError(
-            "Unexpected value for named class definition"
+            "Unexpected value for named class definition; object expected"
         );
     }
 
+    // add the name to the definition
+    def.__name = name;
+
     return extend( def );
 }