How not to leave ISP reset floating?
The ATtiny84 already has an internal pull-up in the order of 50 kilo-ohms, so you really don't need to connect any external components at all.
If you really want to be on the safe side, for example in environment with high electromagnetic interference, you can use an external 10k pull-up if you want.
There is also a hardware getting started application note available which explains best practices how to connect the reset pin under various situations, for example if you are going to use DebugWire or not, or want an external reset button.