I think the issue is with the use of "Target" field. As you can see in from
http://www.soapui.org/Scripting-Propert ... dlers.html:
* Target : an regex filter expression that will be applied for the corresponding target object when the event is triggered. Use this to narrow own invocations. This field can also contain property-expansions (see more below)
So you can't just through in true/false in there. If your AMF steps have common part of step name, you could use "/*AMF*/" as target. But you may have to just surround your filter code with the working if statement:
if(testStepResult instanceof com.eviware.soapui.impl.wsdl.teststeps.AMFTestStepResult) ...
Thanks,
Michael Giller
SmartBear Software