jira 审批功能报错求助，麻烦各位牛人指点

[yangmin3355770]

上周在jira官网试用Script Runner插件，实现了并联审批功能。电子流的设计http://www.xuebuyuan.com/2018423.html这个网页上学习的。今天使用审批功能时就报错了 一直找不出原因，请各位指点帮忙指点下 。报错如下：
Technical details
Log's referral number: 26177611-92c5-4229-9b35-632e18070ae5
Cause
Referer URL: http://192.168.19.31/browse/FEEDBACK-363
Assertion failed:

assert (customField!=null)
| |
null false
Assertion failed:

assert (customField!=null)
| |
null false

at Script1.run(Script1.groovy:27)
at com.onresolve.scriptrunner.runner.ScriptRunnerImpl.runStringAsScript(ScriptRunnerImpl.groovy:155)
at com.onresolve.scriptrunner.runner.ScriptRunner$runStringAsScript$1.call(Unknown Source)
at com.onresolve.scriptrunner.canned.jira.utils.ConditionUtils.processCondition(ConditionUtils.groovy:110)
at com.onresolve.scriptrunner.canned.jira.workflow.postfunctions.AddWatcher.doScript(AddWatcher.groovy:47)