Python syntax error in current_drive.py [BUG]

[mkovari]

The wrong function is used for arctan in cfnbi in current_drive.py.

Steps to reproduce

By mistake I ran PROCESS with an empty input file and it obviously ran using an option that isn't typically tested.

Evidence

File "/home/mkovari/PROCESS/process/current_drive.py", line 1966, in cfnbi
    t2 = 2.0e0 * np.sqrt(3.0e0) * (np.atan(thx) + np.pi / 6.0e0)
...
AttributeError: module 'numpy' has no attribute 'atan'

Environment

Ubuntu in WSL
Tag No. : v3.0.2-27-ga422025