examples/ex1.html fails: RuntimeWarning: invalid value encountered in double_scalars

[yurivict]

https://esa.github.io/pykep/examples/ex1.html

Exit condition -- ftol < 1e-06
/usr/local/lib/python3.7/site-packages/pykep/trajopt/_pl2pl_N_impulses.py:192: RuntimeWarning: invalid value encountered in double_scalars
  DV_list = [s / maxDV * 30 for s in DV_list]
/usr/local/lib/python3.7/site-packages/pykep/trajopt/_pl2pl_N_impulses.py:228: RuntimeWarning: divide by zero encountered in double_scalars
  color='k', s=min(DV1 / maxDV * 30, 40))
/usr/local/lib/python3.7/site-packages/pykep/trajopt/_pl2pl_N_impulses.py:230: RuntimeWarning: divide by zero encountered in double_scalars
  r_target[2] / AU, color='k', s=min(DV2 / maxDV * 30, 40))
/usr/local/lib/python3.7/site-packages/pykep/trajopt/_pl2pl_N_impulses.py:192: RuntimeWarning: invalid value encountered in double_scalars
  DV_list = [s / maxDV * 30 for s in DV_list]
/usr/local/lib/python3.7/site-packages/pykep/trajopt/_pl2pl_N_impulses.py:228: RuntimeWarning: divide by zero encountered in double_scalars
  color='k', s=min(DV1 / maxDV * 30, 40))
/usr/local/lib/python3.7/site-packages/pykep/trajopt/_pl2pl_N_impulses.py:230: RuntimeWarning: divide by zero encountered in double_scalars
  r_target[2] / AU, color='k', s=min(DV2 / maxDV * 30, 40))
/usr/local/lib/python3.7/site-packages/pykep/trajopt/_pl2pl_N_impulses.py:192: RuntimeWarning: invalid value encountered in double_scalars
  DV_list = [s / maxDV * 30 for s in DV_list]
/usr/local/lib/python3.7/site-packages/pykep/trajopt/_pl2pl_N_impulses.py:228: RuntimeWarning: divide by zero encountered in double_scalars
  color='k', s=min(DV1 / maxDV * 30, 40))
/usr/local/lib/python3.7/site-packages/pykep/trajopt/_pl2pl_N_impulses.py:230: RuntimeWarning: divide by zero encountered in double_scalars
  r_target[2] / AU, color='k', s=min(DV2 / maxDV * 30, 40))
Total DV (m/s):  6195.987224252753
Dvs (m/s):  [0.0, 3477.677263059147, 2718.3099611936054]
Tofs (days):  [340.93538876143396, 165.39809089531414]