pop-up error message

[jparish3]

Uncaught TypeError: Cannot read property 'on' of undefined
at i.addTo (popup.js:94)
at HTMLElement._attachedPopup (mapbox-gl-popup.js:312)
at Object.runMethodEffect [as fn] (property-effects.html:904)
at runEffectsForProperty (property-effects.html:168)
at runEffects (property-effects.html:130)
at HTMLElement._propertiesChanged (property-effects.html:1899)
at HTMLElement._flushProperties (properties-changed.html:373)
at HTMLElement._flushProperties (property-effects.html:1731)
at HTMLElement.ready (property-effects.html:1847)
at HTMLElement.ready (element-mixin.html:596)