🐛 ZeroDivisionError in stresscl with i_tf_bucking in {2, 3} #4635

Describe the bug

A ZeroDivisionError occurs in stresscl with i_tf_bucking in {2, 3}.

Steps to reproduce

Change st_regression.IN.DAT i_tf_bucking = 2 and observe.

Expected behaviour

Evidence

    self.models.croco_sctfcoil.run()
  File "/home/matti/code/PROCESS_PROJECT/PROCESS/process/models/tfcoil/superconducting.py", line 4077, in run
    ) = self.stresscl(
        ^^^^^^^^^^^^^^
ZeroDivisionError: division by zero

Environment

• OS: Ubuntu 24
• Version: main

Additional context

This is in a jitted function, and this error goes away when you remove the JIT compilation. This is because a numpy error is raised instead. The problem, however, persists.

I believe it is because a_cs_poloidal is used prior to be being calculated and so it takes a default value of 0.0