If you did a addon a you've broken the addon settings - so you can't delete you addon anymore - try this... Open your WebIDE and open the "Settings" app on your phone ... Go to the Command Prompt and enter:

delete_addon.js

var AddonManager = require('modules/addon_manager');
console.log(AddonManager.addons.array);
// Look for Array [ { _app: { manifestURL: 'app://45ba8d82-cb9b-46de-8cb4-5911a9167353/manifest.webapp' } } ]
AddonManager.findAddonByManifestURL('app://45ba8d82-cb9b-46de-8cb4-5911a9167353/manifest.webapp').then((addon) => { AddonManager.deleteAddon(addon); });