我创建一个多实例用户任务，并将循环基数设置为5。它创建5个并行用户任务。但是我只想完成其中一个用户任务，然后显示：
org.activiti.engine.ActivitiIllegalArgumentException: completionCondition 'All' does not evaluate to a boolean value
at org.activiti.engine.impl.bpmn.behavior.MultiInstanceActivityBehavior.completionConditionSatisfied(MultiInstanceActivityBehavior.java:209)
at org.activiti.engine.impl.bpmn.behavior.ParallelMultiInstanceBehavior.leave(ParallelMultiInstanceBehavior.java:125)
at org.activiti.engine.impl.bpmn.behavior.AbstractBpmnActivityBehavior.leave(AbstractBpmnActivityBehavior.java:49)
at org.activiti.engine.impl.bpmn.behavior.UserTaskActivityBehavior.signal(UserTaskActivityBehavior.java:147)
at org.activiti.engine.impl.bpmn.behavior.MultiInstanceActivityBehavior.signal(MultiInstanceActivityBehavior.java:107)
at org.activiti.engine.impl.persistence.entity.ExecutionEntity.signal(ExecutionEntity.java:407)
at org.activiti.engine.impl.persistence.entity.TaskEntity.complete(TaskEntity.java:201)
at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:50)
at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:24)
at org.activiti.engine.impl.cmd.NeedsActiveTaskCmd.execute(NeedsActiveTaskCmd.java:59)
at org.activiti.engine.impl.interceptor.CommandInvoker.execute(CommandInvoker.java:24)
at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:57)
at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:31)
at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:40)
at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:35)
at org.activiti.engine.impl.TaskServiceImpl.complete(TaskServiceImpl.java:175)
at main.MyFirstActiviti.main(MyFirstActiviti.java:67)