Adopt mf_correlated fields to new domain distributor

nifty5/library/correlated_fields.py

@@ -79,10 +79,11 @@ def make_mf_correlated_field(s_space_spatial, s_space_energy,
     pd_energy = PowerDistributor(pd_spatial.domain, p_space_energy, 1)
     pd = pd_spatial*pd_energy
 
-    dom_distr_0 = DomainDistributor(pd.domain, 0)
-    dom_distr_1 = DomainDistributor(pd.domain, 1)
-    a_spatial = dom_distr_1(amplitude_model_spatial)
-    a_energy = dom_distr_0(amplitude_model_energy)
+    dom_distr_spatial = DomainDistributor(pd.domain, 0)
+    dom_distr_energy = DomainDistributor(pd.domain, 1)
+
+    a_spatial = dom_distr_spatial(amplitude_model_spatial)
+    a_energy = dom_distr_energy(amplitude_model_energy)
     a = a_spatial*a_energy
     A = pd(a)