Fixup gig energy

nifty6/operators/energy_operators.py

@@ -133,6 +133,10 @@ class VariableCovarianceGaussianEnergy(EnergyOperator):
         res0 = x[self._r].vdot(x[self._r]*x[self._icov]).real
         res1 = x[self._icov].log().sum()
         res = 0.5*(res0-res1)
+        if not isinstance(x, Linearization):
+            return Field.scalar(res)
+        if not x.want_metric:
+            return res
         mf = {self._r: x.val[self._icov], self._icov: .5*x.val[self._icov]**(-2)}
         metric = makeOp(MultiField.from_dict(mf))
         return res.add_metric(SandwichOperator.make(x.jac, metric))