interpolation issue in ResolvedCluster()

[rpoleski]

This simple code:

import warnings
warnings.filterwarnings("error", category=RuntimeWarning)
from spisea.imf import imf
from spisea import synthetic
import numpy as np

isochrone = synthetic.IsochronePhot(9.83, 0., 10, 0.3)
imf = imf.IMF_broken_powerlaw(np.array([0.11, 0.5, 120.]), np.array([-1.3, -2.3]))
cluster = synthetic.ResolvedCluster(isochrone, imf, 1.0e4)

fails with such an error message:

Traceback (most recent call last):
  File "test.py", line 9, in <module>
    cluster = synthetic.ResolvedCluster(isochrone, imf, 1.0e4)
  File "/.../SPISEA/spisea/synthetic.py", line 162, in __init__
    star_systems = self._make_star_systems_table(mass, isMulti, sysMass)
  File "/.../SPISEA/spisea/synthetic.py", line 219, in _make_star_systems_table
    star_systems['Teff'] = self.iso_interps['Teff'](star_systems['mass'])
  File "/usr/local/lib64/python3.8/site-packages/scipy/interpolate/polyint.py", line 78, in __call__
    y = self._evaluate(x)
  File "/usr/local/lib64/python3.8/site-packages/scipy/interpolate/interpolate.py", line 682, in _evaluate
    y_new = self._call(self, x_new)
  File "/usr/local/lib64/python3.8/site-packages/scipy/interpolate/interpolate.py", line 630, in _call_linear
    slope = (y_hi - y_lo) / (x_hi - x_lo)[:, None]
RuntimeWarning: divide by zero encountered in true_divide

Changing age from 9.83 to 9.8 solves the error but I'm guessing there is some deeper bug.