BUG: Attributes in the body tag are incorrectly handled

Description/Steps to reproduce

When adding attributes to the body tag (e.g. <soap:Body soap:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">), the library currently returns the following error:

TypeError: Cannot read properties of undefined (reading 'output')
at Server._executeMethod (/usr/src/app/node_modules/strong-soap/src/server.js:337:44)
at Server._process (/usr/src/app/node_modules/strong-soap/src/server.js:207:14)
at IncomingMessage. (/usr/src/app/node_modules/strong-soap/src/server.js:112:18)
at IncomingMessage.emit (node:events:513:28)
at endReadableNT (node:internal/streams/readable:1359:12)
at process.processTicksAndRejections (node:internal/process/task_queues:82:21)

Currently, this was only supported using the document style and when the attributes key was set to the default "attributes". If the rpc style is used or a different attributesKey is set up, this is not supported.

Expected result

Adding attributes to the body tag of the request should not result in an error and rather return the same as a call without any attributes in the body tag.

Additional information

linux x64 20.12.2
npm WARN config production Use --omit=dev instead.

Start in src/server.js at the _executeMethod and _process paths shown in the error trace, then reproduce a SOAP request with attributes on the body tag. Compare document and rpc styles and the default versus custom attributesKey behavior. Done means the request no longer errors and returns the same result as the equivalent request without body attributes.