Improve error handling in partial AppMap

When limiting root events to HTTP, nothing is displayed in the trace view:

Also while root events are limited to HTTP, HelloWorldServer$HelloWorldHandler is missing from the dependency map:

Toggling Limit root events to HTTP off displays the desired results in the dependency map:

However the HTTP server request is still missing from the trace view:

Below is the AppMap described. It's worth noting that two of the three events in the AppMap do not return:

• http_server_request - no return
• HelloWorldHandler#handle - no return
• HelloWorldHandler#sayHello - returns

It's likely that the missing returns here are causing issues. The AppMap client should be able to gracefully handle cases where such data is missing.
hw.appmap.json.txt