[vjets] ensure correct shape for sf

tasks/corrections/vjets.py

@@ -256,7 +256,7 @@ class VptSF:
         if nlo:
             nlo = self.nlo(dataset, LHE.Vpt, LHE.Nb, shifts=True)
             if nlo is None:
-                sf = np.ones_like(LHE.Vpt)
+                sf = np.ones((len(events.MET),))
                 shift = 0
             else:
                 sf, shift = nlo