Extension is not working in Firefox 26

[MelkorNemesis]

When using Firefox 26, there're two glitches.

1) TypeError: invalid 'in' operand window.history
[Break On This Error]
this.popped = !!('state' in window.history) && !!window.history.state;

After fixing this line to not use in operand, another glitch occurs.
2) window.history is undefined

Is there any way you can make this work (at least graceful degradation)?

Thanks

[Majkl578]

window.history is undefined? It's not by default, you should probably investigate this.