Remove warning for divide by zero error in mesa quant

[hbeale]

I get a warning message running mesa quant:

Dennis confirmed that dividing by zero is expected behavior for genes that are not expressed. We discussed turning off the warning before the divide statement and turning it back on after.

Calculating PS values...
/mnt/scratch/splicedice/splicedice_env/lib/python3.12/site-packages/mesa/MESA.py:306: RuntimeWarning: invalid value encountered in divide
  psi[self.junctionIndex[junction],:] = inclusions / (inclusions + exclusions)
        Done [0:00:1.28]