this.order is undefined in UnitAI FindWalkAndFightTargets

[elexis]

We got this UnitAI error in an svn match with r21635 (just after ​Phab:D1419, don't know if it's related.)

ERROR: Error in timer on entity 3483, IID95, function TimerHandler: TypeError: this.order is undefined
  UnitAI.prototype.FindWalkAndFightTargets@simulation/components/UnitAI.js:5450:1
  UnitAI.prototype.UnitFsmSpec.INDIVIDUAL.COMBAT.ATTACKING.Timer@simulation/components/UnitAI.js:1983:8
  FSM.prototype.ProcessMessage@simulation/helpers/FSM.js:274:12
  UnitAI.prototype.TimerHandler@simulation/components/UnitAI.js:3859:2
  Timer.prototype.OnUpdate@simulation/components/Timer.js:120:4

ERROR: Error in timer on entity 3488, IID95, function TimerHandler: TypeError: this.order is undefined
  UnitAI.prototype.FindWalkAndFightTargets@simulation/components/UnitAI.js:5450:1
  UnitAI.prototype.UnitFsmSpec.INDIVIDUAL.COMBAT.ATTACKING.Timer@simulation/components/UnitAI.js:1983:8
  FSM.prototype.ProcessMessage@simulation/helpers/FSM.js:274:12
  UnitAI.prototype.TimerHandler@simulation/components/UnitAI.js:3859:2
  Timer.prototype.OnUpdate@simulation/components/Timer.js:120:4

[elexis]

(error spammed every JB match)

[temple]

In 21655:

Formation members shouldn't use IsWalkingAndFighting

Differential Revision: ​https://code.wildfiregames.com/D1425
Comments by: mimo, bb
Fixes: #5108

[elexis]

Thanks