Replace Wakefield which no longer exists in xfields by Waketracker

Author: xbuffat

xwakes/wit/component.py

@@ -233,7 +233,7 @@ def configure_for_tracking(self, zeta_range: Tuple[float, float],
                                **kwargs # for multibuunch compatibility
                                ) -> None:
         import xfields as xf
-        self._xfields_wf = xf.Wakefield(components=[self], zeta_range=zeta_range,
+        self._xfields_wf = xf.WakeTracker(components=[self], zeta_range=zeta_range,
                                         num_slices=num_slices, **kwargs)
 
     def track(self, particles):
@@ -794,6 +794,7 @@ def function_vs_t(self, t, beta0, dt):
 
         if isscalar:
             out = out[0]
+            
         return out
 
     @staticmethod