Remove the second class from the icons property

[RndFooBar]

Adding a Button with two icons propriety (like here) causes this error.
Detailled explanation.

[yuleugim]

Can confirm on the latest tokamak version 0.2.7, and tool-bar version 1.0.0

The issue here is that tokamak is not adhering to tool-bar's .addButton method syntax. Proper usage of the method is documented here: https://github.com/suda/tool-bar/blob/master/README.md

So instead of:

@toolBar.addButton
      icon: 'ion ion-hammer'
      callback: 'tokamak:build'
      tooltip: 'Build'

There should be no prefixes and the icon set should be called separately:

@toolBar.addButton
      icon: 'hammer'
      callback: 'tokamak:build'
      tooltip: 'Build'
      iconset: 'ion'

Doing this for all of the non-Octicons icons (the default icon set for tool-bar) fixed it for me.

[dizergin]

yuleugim , it works for me too. so it looks like a tokamak's bug.