Fix normalization for the special boundary points

Need to normalise by the sum of weights obviously
(otherwise would leads to crazy low values of the phase field
in random points of the domain)

models/multiphase/d3q27_pf_velocity/Boundary.c.Rt

@@ -781,17 +781,19 @@ CudaDeviceFunction void calcWallPhase_correction() {
             int count = 0;
             real_t fluid_average = 0.0;
             real_t x, y, z;
+            real_t denom = 0.0;
 			for (int i=1; i<27 ; i++){
 				x = d3q27_ex[i];
 				y = d3q27_ey[i];
 				z = d3q27_ez[i];
                 if (!IsBoundary_dyn(int(x), int(y), int(z)) && PhaseF_dyn(int(x), int(y), int(z)) > -0.5) {
                     fluid_average += wg[i]*PhaseF_dyn(int(x), int(y), int(z));
+                    denom += wg[i];
                     count++;
                 }
 			}
             // print sum and average and count
-            PhaseF = count == 0 ? 1 : fluid_average / count;
+            PhaseF = count == 0 ? 1 : fluid_average / denom;
         } else {
             PhaseF = point_in_the_normal_direction;
         }