second round of making per-atom allocations consistent.

now all sections that dimension per-atom local arrays to atom->nmax
will also *test* for atom->nmax and thus we avoid potential segfaults
in all cases where atom->nlocal or atom->nlocal+atom->nghost are 0.
it doesn't make sense to test for these if the arrays are dimensioned
to atom->nmax afterwards anyway.

src/fix_move.cpp

@@ -726,7 +726,7 @@ void FixMove::initial_integrate(int vflag)
 
     // reallocate displace and velocity arrays as necessary
 
-    if ((displaceflag || velocityflag) && nlocal > maxatom) {
+    if ((displaceflag || velocityflag) && atom->nmax > maxatom) {
       maxatom = atom->nmax;
       if (displaceflag) {
         memory->destroy(displace);