Fixes segfault due to uninitialized pointers

{

  ewaldflag = pppmflag = 1;

  writedata = 1;

  ftable = NULL;

  ftable = nullptr;

  cut_lj = nullptr;

  cut_ljsq = nullptr;

  a = nullptr;

  rho = nullptr;

  c = nullptr;

  rhoinv = nullptr;

  buck1 = nullptr;

  buck2 = nullptr;

  offset = nullptr;

  cut_respa = nullptr;

}

/* ---------------------------------------------------------------------- */