Walkthrough doesn't start, causes JS error

[quincylvania]

Upon clicking "Start the Walkthrough", either from the welcome screen or from the help tab, this error occurs.

[Error] TypeError: e.layer.enabled is not a function. (In 'e.layer.enabled("osm"===e.id)', 'e.layer.enabled' is undefined)
	(anonymous function) (id-fce7f73222b17805b5c70e316de43b738b8e29cf1a2c5870691c4ef69f15b1bc.js:15:29210)
	forEach
	e (id-fce7f73222b17805b5c70e316de43b738b8e29cf1a2c5870691c4ef69f15b1bc.js:15:29182)
	selection_call (id-fce7f73222b17805b5c70e316de43b738b8e29cf1a2c5870691c4ef69f15b1bc.js:1:12977)
	o (id-fce7f73222b17805b5c70e316de43b738b8e29cf1a2c5870691c4ef69f15b1bc.js:16:14170)
	(anonymous function) (id-fce7f73222b17805b5c70e316de43b738b8e29cf1a2c5870691c4ef69f15b1bc.js:1:18621)