Move the generation of particle output at the right position (python)

bfps/NSVorticityEquation.py

@@ -620,13 +620,13 @@ class NSVorticityEquation(_fluid_particle_base):
             args = [],
             **kwargs):
         opt = self.prepare_launch(args = args)
-        self.fill_up_fluid_code()
         if opt.nparticles > 0:
             self.name += '-particles'
             self.add_particles(
                 integration_steps = 4,
                 neighbours = opt.neighbours,
                 smoothness = opt.smoothness)
+        self.fill_up_fluid_code()
         self.finalize_code()
         self.launch_jobs(opt = opt)
         return None