Describe the bug
It should be impossible to instantiate a PVSystem with no Arrays. Currently this is possible via PVSystem(arrays=[]).
To Reproduce
Steps to reproduce the behavior:
from pvlib import pvsystem
pvsystem.PVSystem(arrays=[])
results in this PVSystem:
PVSystem:
name: None
inverter: None
Expected behavior
A ValueError should be raised indicating that a PVSystem must have at least one Array and suggesting that a system with an arbitrary default array can be constructed by passing arrays=None or not passing the arrays parameter at all.
Versions:
pvlib.__version__: 0.8.1+