********> bugfix.18
Author:  Dave Case
Date:    5/30/00

Programs: sander

Description: The input combination of ntb=0 and igb=0 is illegal, but
             the error message in this case is very confusing.  The
             patch below should help.

Fix:  Make the following change to src/sander/mdread.f
----------------------------------------------------------------------------
*** mdread.f.old        Tue May 30 17:36:35 2000
--- mdread.f    Tue May 30 17:37:41 2000
***************
*** 289,296 ****
  c If user has requested ewald electrostatics, read some more input
  c--------------------------------------------------------------------
  c
!       if( igb .eq. 0 ) call load_ewald_info(5,parm,inpcrd,ntx,r_stack,
!      $      ipol)
  C
        NRCP = NTR
        ISHAKE = 0
--- 289,296 ----
  c If user has requested ewald electrostatics, read some more input
  c--------------------------------------------------------------------
  c
!       if( igb.eq.0 .and. ntb.gt.0 ) 
!      $    call load_ewald_info(5,parm,inpcrd,ntx,r_stack,ipol)
  C
        NRCP = NTR
        ISHAKE = 0
***************
*** 1001,1007 ****
          inerr = 1
        endif
        if (ntb.eq.0 .and. igb.eq.0 ) then
!         write(6,'(/,a)') ' Ewald calculation must have ntb>0'
          inerr = 1
        endif
        if (ntb.ne.0 .and. igb.gt.0 ) then
--- 1001,1007 ----
          inerr = 1
        endif
        if (ntb.eq.0 .and. igb.eq.0 ) then
!         write(6,'(/,a)') ' igb=0 is only compatible with ntb>0'
          inerr = 1
        endif
        if (ntb.ne.0 .and. igb.gt.0 ) then
----------------------------------------------------------------------------