pyzx unable to optimize when circuit contains rx or sx gate

Using the most recent version of pyzx (0.8.0), with the following code
```Python
import pyzx as zx
from pyzx.circuit import Circuit, CNOT
c = Circuit(1)
c.add_gate('XPhase', 0, phase=3/4)
zx.draw(c)
zx.full_optimize(c.to_basic_gates())
```
and it returns with an error
" Unknown gate XPhase(0,phase=0.75). Maybe simplify the gates with circuit.to_basic_gates()? "