default pbar in SequentialRK4IP

src/scgenerator/physics/simulate.py

@@ -224,10 +224,10 @@ class SequentialRK4IP(RK4IP):
     def __init__(
         self,
         params: Parameters,
-        pbars: PBars,
+        pbars: PBars = None,
         save_data=False,
     ):
-        self.pbars = pbars
+        self.pbars = pbars or PBars(params.z_num, f"Simulating {params.name}", 1)
         super().__init__(
             params,
             save_data=save_data,