Javascript TypeError when using Leaflet.js

Question

I'm using the icingaweb2 nagvis module, which uses Leaflet to show a world map. Most things work, but when I click on the map, the following error is shown:

Javascript error occured: Uncaught TypeError: Cannot read property 'call' of undefined h t t p : / / icingaweb2.server/nagvis/frontend/nagvis-js/js/ExtLeaflet.js?v=1.9b12 (5)

I'm using version Leaflet 1.0.3+ed36a04 of Leaflet.

Inspecting the error in Chrome:

VM184 ExtLeaflet.js?v=1.9b12:5 Uncaught TypeError: Cannot read property 'call' of undefined

    at e.fire (VM184 ExtLeaflet.js?v=1.9b12:5)
    at e._fireDOMEvent (VM184 ExtLeaflet.js?v=1.9b12:6)
    at e._handleDOMEvent (VM184 ExtLeaflet.js?v=1.9b12:6)
    at HTMLDivElement.h (VM184 ExtLeaflet.js?v=1.9b12:6)

Can someone please help me fix the error?