Model not in Materials Project error

If a combination of elements has no models in the Materials Project, a ValueError occurs
```py
pi = PhaseIdentification()
pi.find_phase_nn(apikey='', elementList=['F', 'Na', 'Li'], fileName='', cutDataStart=1, q_dep_shift=1.0, const_shift=0.0)
```
Error:
```py
ValueError: max() args is an empty sequence
```