To reproduce, make a simple Aura with Status - Cooldown progress (spell) using a spell with charges (I tested with Blink on Mage and Barbed Shot on Hunter)
In Display use %charges %maxCharges
The text will be, for example, 2 2
Now use the ability a couple of times until the last charge is on CD.
The text will be 0

the specific reason this came up was someone using aura_env.state.maxCharges in a custom text function but I think it's reasonable for people to want maxCharges to show throughout on any spell that has charges.

I think this is due to b81a169

Fixed for the next release.