message: Replaced default value for redirectURL
  Linter will not allow null to be the default value for redirectURL.
diff: @@ -160,10 +160,10 @@ export function loadUserData() {
  * @param {String} [redirectURL=null] Location to redirect user to after sign out.
  * @return {void}
  */
  -export function signUserOut(redirectURL: string = null) {
  +export function signUserOut(redirectURL: string = '') {
  window.localStorage.removeItem(BLOCKSTACK_STORAGE_LABEL)
  - if (redirectURL !== null) {
  + if (redirectURL !== '') {
  window.location = redirectURL
  }
  }
  