setError (error, child) {
    this.error = error
    this.errorChild = child

    if (this.dom && this.dom.tr) {
      this.updateError()
    }
  }
@param {{dataPath: string, keyword: string, message: string, params: Object, schemaPath: string} | null} error
@param {Node} [child]  When this is the error of a parent node, pointing
                       to an invalid child node, the child node itself
                       can be provided. If provided, clicking the error
                       icon will set focus to the invalid child node.