Number of collisions per collision pair

Now the number of collisions is calculated per species pair. This allows
that the randomly particles selected for collisions do not have
collisions assigned.

src/modules/mesh/0D/moduleMesh0D.f90

@@ -63,6 +63,7 @@ MODULE moduleMesh0D
     !Inits dummy 0D volume
     SUBROUTINE initVol0D(self, n, p, nodes)
       USE moduleRefParam
+      USE moduleSpecies
       IMPLICIT NONE
 
       CLASS(meshVol0D), INTENT(out):: self
@@ -80,6 +81,9 @@ MODULE moduleMesh0D
 
       CALL OMP_INIT_LOCK(self%lock)
 
+      ALLOCATE(self%listPart_in(1:nSpecies))
+      ALLOCATE(self%totalWeight(1:nSpecies))
+
     END SUBROUTINE initVol0D
 
     PURE FUNCTION getNodes0D(self) RESULT(n)