fix

python/time_integration.py

@@ -42,7 +42,8 @@ def _advance_particles(particles, f, dt, min_nsub,contact_tol,max_nsub=None,afte
         vn = v + f*dt / particles.mass()
         vmax = np.max(np.linalg.norm(vn,axis=1))
         nsub = max(min_nsub, int(np.ceil((vmax * dt * 8)/min(particles.r()))))
-        nsub = min(max_nsub, nsub)
+        if max_nsub is not None :
+            nsub = min(max_nsub, nsub)
     else:
         nsub = 1
         vmax = 0