Fix an issue in assigning cells in ionization Boundary

This assigns the correct random cell when a particle is created from the
ionization boundary.

Also, the number of possible ionizations is reduced by one if there is a
suscesful ionization. This has no impact on the results.

src/modules/mesh/moduleMeshBoundary.f90

@@ -156,8 +156,14 @@ MODULE moduleMeshBoundary
             newElectron%r = edge%randPos()
             newIon%r      = newElectron%r
 
-            newElectron%cell = part%cell
-            newIon%cell      = part%cell
+            IF (ASSOCIATED(edge%e1)) THEN
+              newElectron%cell = edge%e1%n
+
+            ELSEIF (ASSOCIATED(edge%e2)) THEN
+              newElectron%cell = edge%e2%n
+
+            END IF
+            newIon%cell      = newElectron%cell
 
             newElectron%Xi = mesh%cells(part%cell)%obj%phy2log(newElectron%r)
             newIon%Xi      = newElectron%Xi
@@ -178,6 +184,9 @@ MODULE moduleMeshBoundary
             eRel = eRel - bound%eThreshold
             vRel = 2.D0*DSQRT(eRel)/mRel
 
+            !Reduce number of possible ionizations
+            nIonizations = nIonizations - 1
+
           END IF
 
         END DO