Add issue to Mantis system

i used mcp.mc_issue_add() to add issue into Mantis system, issue was added, but Log viewer show a error “org.codehaus.groovy.runtime.InvokerInvocationException: Error Type: SYSTEM NOTICE,
Error Description: Undefined variable: t_message”
i couldn’t find variable: t_message anywhere in my code.
How can i fix it ?
So many thank.