Error when variable names contains numbers

[IgnacioVellido]

When a variable defined in the configuration file (or generally, in the game) contains a number the following error is returned:

Exception in thread "main" java.lang.NullPointerException 
at controller.PlanningAgent.translateGameStateToPDDL(PlanningAgent.java:634)
at controller.PlanningAgent.act(PlanningAgent.java:207
at ontology.avatar.MovingAvatar.requestPlayerInput(MovingAvatar.java:135)
at ontology.avatar.MovingAvatar.updateAvatar(MovingAvatar.java:103)
at ontology.avatar.oriented.OrientedAvatar.updateAvatar(OrientedAvatar.java:53)
at core.game.Game.tick(Game.java:1363)
at core.game.Game.gameCycle(Game.java:1101)
at core.game.Game.runGame(Game.java:873)
at tracks.ArcadeMachine.runOneGame(ArcadeMachine.java:168)
at tracks.singlePlayer.Test.main(Test.java:83)             

For example, when giving the configuration file:

gameElementsCorrespondences:
...
  inc1:
  - (at ?x ?y ?inc1)
  inc2:
  - (at ?x ?y ?inc2)
  inc3:
  - (at ?x ?y ?inc3)
  inc4:
  - (at ?x ?y ?inc4)
  inc5:
  - (at ?x ?y ?inc5)
  inc6:
  - (at ?x ?y ?inc6)

variablesTypes:
  ?inc1: inc1
  ?inc2: inc2
  ?inc3: inc3
  ?inc4: inc4
  ?inc5: inc5
  ?inc6: inc6

Renaming the variables (in the VGDL file and in the config) misses the error:

gameElementsCorrespondences:
...
  inca:
  - (at ?x ?y ?inca)
  incb:
  - (at ?x ?y ?incb)
  incc:
  - (at ?x ?y ?incc)
  incd:
  - (at ?x ?y ?incd)
  ince:
  - (at ?x ?y ?ince)
  incf:
  - (at ?x ?y ?incf)

variablesTypes:
  ?inca: inca
  ?incb: incb
  ?incc: incc
  ?incd: incd
  ?ince: ince
  ?incf: incf