Program: 89026
Project: 89026
Buggy source:
private Collection<ResourceHolder> handleEntityDeath(EntityDeathEvent event,LivingEntity entity,Player killer){
  boolean hasKiller=(killer != null);
  Integer id=entity.getEntityId();
  Configuration config=null;
  Action action=null;
  List<ResourceHolder> generated=null;
  Collection<ResourceHolder> result=null;
  if (scheduledRewards.containsKey(id)) {
    FutureReward future=scheduledRewards.get(id);
    if (future != null) {
      action=future.action;
      generated=future.generated;
      config=future.config;
    }
    scheduledRewards.remove(id);
  }
 else {
    config=getConfiguration(entity,killer);
    if (config != null) {
      action=getAction(config,entity,killer);
      RewardProvider rewards=config.getRewardProvider();
      if (action != null)       generated=action.generateRewards(rewards,random);
    }
  }
  if (generated != null) {
    ChannelProvider channels=config.getChannelProvider();
    RewardProvider rewards=config.getRewardProvider();
    event.setDroppedExp(0);
    result=action.rewardAnyone(rewards,entity.getWorld(),generated,entity.getLocation());
    config.getMessageQueue().enqueue(null,action,channels.getFormatter(null,result));
    if (hasDebugger())     debugger.printDebug(this,"String_Node_Str",id,StringUtils.join(result,"String_Node_Str"));
  }
 else   if (config.isDefaultRewardsDisabled() && hasKiller) {
    event.setDroppedExp(0);
    if (hasDebugger())     debugger.printDebug(this,"String_Node_Str",id);
  }
 else   if (!config.isDefaultRewardsDisabled() && hasKiller) {
    int expDropped=event.getDroppedExp();
    if (config.getMultiplier() != 1) {
      SampleRange increase=new SampleRange(expDropped * config.getMultiplier());
      int expChanged=increase.sampleInt(random);
      event.setDroppedExp(expChanged);
      if (hasDebugger())       debugger.printDebug(this,"String_Node_Str",id,expChanged);
    }
  }
  if (!(entity instanceof Player)) {
    spawnReasonLookup.remove(id);
  }
  if (result == null) {
    result=Lists.newArrayList((ResourceHolder)new ExperienceHolder(event.getDroppedExp()));
  }
  return null;
}

Fixed version (ground truth):
private Collection<ResourceHolder> handleEntityDeath(EntityDeathEvent event,LivingEntity entity,Player killer){
  boolean hasKiller=(killer != null);
  Integer id=entity.getEntityId();
  Configuration config=null;
  Action action=null;
  List<ResourceHolder> generated=null;
  Collection<ResourceHolder> result=null;
  if (scheduledRewards.containsKey(id)) {
    FutureReward future=scheduledRewards.get(id);
    if (future != null) {
      action=future.action;
      generated=future.generated;
      config=future.config;
    }
    scheduledRewards.remove(id);
  }
 else {
    config=getConfiguration(entity,killer);
    if (config != null) {
      action=getAction(config,entity,killer);
      RewardProvider rewards=config.getRewardProvider();
      if (action != null)       generated=action.generateRewards(rewards,random);
    }
  }
  if (hasDebugger())   debugger.printDebug(this,"String_Node_Str",ToStringBuilder.reflectionToString(generated));
  if (generated != null) {
    ChannelProvider channels=config.getChannelProvider();
    RewardProvider rewards=config.getRewardProvider();
    event.setDroppedExp(0);
    if (killer != null)     result=action.rewardPlayer(rewards,killer,generated);
 else     result=action.rewardAnyone(rewards,entity.getWorld(),generated,entity.getLocation());
    config.getMessageQueue().enqueue(null,action,channels.getFormatter(null,result));
    if (hasDebugger())     debugger.printDebug(this,"String_Node_Str",id,StringUtils.join(result,"String_Node_Str"));
  }
 else   if (config.isDefaultRewardsDisabled() && hasKiller) {
    event.setDroppedExp(0);
    if (hasDebugger())     debugger.printDebug(this,"String_Node_Str",id);
  }
 else   if (!config.isDefaultRewardsDisabled() && hasKiller) {
    int expDropped=event.getDroppedExp();
    if (config.getMultiplier() != 1) {
      SampleRange increase=new SampleRange(expDropped * config.getMultiplier());
      int expChanged=increase.sampleInt(random);
      event.setDroppedExp(expChanged);
      if (hasDebugger())       debugger.printDebug(this,"String_Node_Str",id,expChanged);
    }
  }
  if (!(entity instanceof Player)) {
    spawnReasonLookup.remove(id);
  }
  if (result == null) {
    result=Lists.newArrayList((ResourceHolder)new ExperienceHolder(event.getDroppedExp()));
  }
  return null;
}