Looks like the SOAP gateway expects the style attribute to be present in the soap:binding definition of a WSDL. It's optional at this level and can be present on individual operations. See this for detail:

http://www.w3.org/TR/wsdl#_soap:binding

Here's the error when using a WSDL with no style attribute at the soap:binding level:

Caused by: java.lang.NullPointerException
at org.switchyard.component.soap.util.WSDLUtil.getStyle(WSDLUtil.java:242)
at org.switchyard.component.soap.OutboundHandler.start(OutboundHandler.java:89)
at org.switchyard.deploy.internal.Deployment.deployReferenceBindings(Deployment.java:283)
at org.switchyard.deploy.internal.Deployment.start(Deployment.java:139)
at org.switchyard.as7.extension.deployment.SwitchYardDeployment.start(SwitchYardDeployment.java:106)
at org.switchyard.as7.extension.services.SwitchYardService.start(SwitchYardService.java:78)