BuildMovePeonZeppelin bug

[jzy-chitong56]

https://github.com/SMUnlimited/AMAI/blob/96800f004d3a1ba2d891fa9cbfacaa840401f420/common.eai#L9577

set build_zeppelin = GetUnusedZeppelinNearUnit(peon)
// Disabled just in case
set build_zeppelin = null
if build_zeppelin == null then
  call Trace("No Zeppelin found for transporting peon")
  return false
endif

**if build_zeppelin == null then**

but build_zeppelin is null now , set build_zeppelin = null

---

function BuildMovePeonZeppelin takes unit peon, unit target returns boolean
  if build_zeppelin == null or not UnitAlive(build_zeppelin) then
    set build_zeppelin = GetUnusedZeppelinNearUnit(peon)
	// Disabled just in case
	set build_zeppelin = null
    if build_zeppelin == null then
      call Trace("No Zeppelin found for transporting peon")
      return false
    endif
    call GroupAddUnit(unit_zepplin_move, build_zeppelin)
  endif
  if IsUnitInTransport(peon, build_zeppelin) then
    if DistanceBetweenUnits(build_zeppelin, target) > 300 then
      call IssuePointOrder(build_zeppelin, "move", GetUnitX(target), GetUnitY(target))
    else
      call IssueTargetOrder(build_zeppelin, "unload", peon)
    endif
  else
    if DistanceBetweenUnits(peon, target) < 400 then
      call GroupRemoveUnit(unit_zepplin_move, build_zeppelin)
      set build_zeppelin = null
      return true
    else
      call IssueTargetOrder(peon, "smart", build_zeppelin)
    endif
  endif
  return false
endfunction