Program: 187520
Project: 187520
Buggy source:
@Override public boolean shouldStart(){
  if (!petEntity.canMove()) {
    return false;
  }
  if (myPet.getDamage() <= 0 && myPet.getRangedDamage() <= 0) {
    return false;
  }
  if (this.petEntity.goalTarget == null) {
    return false;
  }
  if (behaviorSkill != null && behaviorSkill.isActive()) {
    if (behaviorSkill.getBehavior() == Behavior.BehaviorState.Friendly) {
      this.petEntity.goalTarget=null;
      return false;
    }
    if (behaviorSkill.getBehavior() == BehaviorState.Raid) {
      if (this.petEntity.goalTarget instanceof EntityTameableAnimal && ((EntityTameableAnimal)this.petEntity.goalTarget).isTamed()) {
        this.petEntity.goalTarget=null;
        return false;
      }
      if (this.petEntity.goalTarget instanceof EntityMyPet) {
        this.petEntity.goalTarget=null;
        return false;
      }
      if (this.petEntity.goalTarget instanceof EntityPlayer) {
        this.petEntity.goalTarget=null;
        return false;
      }
    }
  }
  if (this.petEntity.goalTarget instanceof EntityPlayer) {
    Player targetPlayer=(Player)this.petEntity.goalTarget.getBukkitEntity();
    if (myPet.getOwner().equals(targetPlayer)) {
      this.petEntity.goalTarget=null;
      return false;
    }
 else     if (!PvPChecker.canHurt(myPet.getOwner().getPlayer(),targetPlayer)) {
      this.petEntity.goalTarget=null;
      return false;
    }
  }
 else   if (this.petEntity.goalTarget instanceof EntityTameableAnimal) {
    EntityTameableAnimal tameable=(EntityTameableAnimal)this.petEntity.goalTarget;
    if (tameable.isTamed() && tameable.getOwner() != null) {
      Player tameableOwner=(Player)tameable.getOwner().getBukkitEntity();
      if (myPet.getOwner().equals(tameableOwner)) {
        this.petEntity.goalTarget=null;
        return false;
      }
 else       if (!PvPChecker.canHurt(myPet.getOwner().getPlayer(),tameableOwner)) {
        this.petEntity.goalTarget=null;
        return false;
      }
    }
  }
 else   if (this.petEntity.goalTarget instanceof EntityMyPet) {
    MyPet targetMyPet=((EntityMyPet)this.petEntity.goalTarget).getMyPet();
    if (targetMyPet == null) {
      this.petEntity.goalTarget=null;
      return false;
    }
    if (!PvPChecker.canHurt(myPet.getOwner().getPlayer(),targetMyPet.getOwner().getPlayer())) {
      this.petEntity.goalTarget=null;
      return false;
    }
  }
  this.target=this.petEntity.goalTarget;
  this.petEntity.goalTarget=null;
  return true;
}

Fixed version (ground truth):
@Override public boolean shouldStart(){
  if (!petEntity.canMove()) {
    return false;
  }
  if (myPet.getDamage() <= 0 && myPet.getRangedDamage() <= 0) {
    return false;
  }
  if (this.petEntity.goalTarget == null) {
    return false;
  }
  if (behaviorSkill != null && behaviorSkill.isActive()) {
    if (behaviorSkill.getBehavior() == Behavior.BehaviorState.Friendly) {
      this.petEntity.goalTarget=null;
      return false;
    }
    if (behaviorSkill.getBehavior() == BehaviorState.Raid) {
      if (this.petEntity.goalTarget instanceof EntityTameableAnimal && ((EntityTameableAnimal)this.petEntity.goalTarget).isTamed()) {
        this.petEntity.goalTarget=null;
        return false;
      }
      if (this.petEntity.goalTarget instanceof EntityMyPet) {
        this.petEntity.goalTarget=null;
        return false;
      }
      if (this.petEntity.goalTarget instanceof EntityPlayer) {
        this.petEntity.goalTarget=null;
        return false;
      }
    }
  }
  if (this.petEntity.goalTarget instanceof EntityPlayer) {
    Player targetPlayer=(Player)this.petEntity.goalTarget.getBukkitEntity();
    if (myPet.getOwner().equals(targetPlayer)) {
      this.petEntity.goalTarget=null;
      return false;
    }
 else     if (!PvPChecker.canHurt(myPet.getOwner().getPlayer(),targetPlayer)) {
      this.petEntity.goalTarget=null;
      return false;
    }
  }
 else   if (this.petEntity.goalTarget instanceof EntityTameableAnimal) {
    EntityTameableAnimal tameable=(EntityTameableAnimal)this.petEntity.goalTarget;
    if (tameable.isTamed() && tameable.getOwner() != null) {
      Player tameableOwner=(Player)tameable.getOwner().getBukkitEntity();
      if (myPet.getOwner().equals(tameableOwner)) {
        this.petEntity.goalTarget=null;
        return false;
      }
 else       if (!PvPChecker.canHurt(myPet.getOwner().getPlayer(),tameableOwner)) {
        this.petEntity.goalTarget=null;
        return false;
      }
    }
  }
 else   if (this.petEntity.goalTarget instanceof EntityMyPet) {
    MyPet targetMyPet=((EntityMyPet)this.petEntity.goalTarget).getMyPet();
    if (targetMyPet == null) {
      this.petEntity.goalTarget=null;
      return false;
    }
    if (!PvPChecker.canHurt(myPet.getOwner().getPlayer(),targetMyPet.getOwner().getPlayer())) {
      this.petEntity.goalTarget=null;
      return false;
    }
  }
  if (!PvPChecker.canHurtCitizens(this.petEntity.goalTarget.getBukkitEntity())) {
    return false;
  }
  this.target=this.petEntity.goalTarget;
  this.petEntity.goalTarget=null;
  return true;
}