fix mobs reader template fix (#2031)

mobs/templates/frontend~app~player~web~messages~RawMessageReader.gen.ts.erb

@@ -31,7 +31,6 @@ export default class RawMessageReader extends PrimitiveReader {
 <% end %>
     default:
       throw new Error(`Unrecognizable message type: ${ tp }; Pointer at the position ${this.p} of ${this.buf.length}`)
-      return null;
     }
   }
 }