BugFix: Buggy recording of AppliedEnergy.

  + Appeared if .Integrate(..., relax=True) used after an external field was applied earlier.
  + Computation was already correct before.

integrators/_details/physicalToMathematical.py

@@ -108,7 +108,11 @@ def Compute_Cst(self):
 def ConvertAppliedField(self):
   import types
   from ngsolve import CoefficientFunction, x, y, z
+
   if(self.parameters.H_ext == None):
+    self._hext_cf = CoefficientFunction((0, 0, 0))
+    self._hext_impl_cf = CoefficientFunction((0, 0, 0))
+    self._hext_mp_cf = CoefficientFunction((0, 0, 0))
     return
   
   tScale = self.parameters.gamma0 * self.parameters.Ms