setAttribute(attr, value, componentPropValue) {
    // Check if system exists (i.e. is registered).
    if (_system_js__WEBPACK_IMPORTED_MODULE_4__.systems[attr]) {
      _a_node_js__WEBPACK_IMPORTED_MODULE_8__.ANode.prototype.setAttribute.call(this, attr, value);

      // Update system instance, if initialized on the scene.
      var system = this.systems[attr];
      if (system) {
        system.updateProperties(value);
      }
      return;
    }
    _a_entity_js__WEBPACK_IMPORTED_MODULE_7__.AEntity.prototype.setAttribute.call(this, attr, value, componentPropValue);
  }
Wrap Entity.setAttribute to take into account for systems.
If system exists, then skip component initialization checks and do a normal
setAttribute.