[BUG] Title #323

Prerequisites

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Description

[Description of the issue]

Steps to Reproduce

1. start server
   httpserver::webserver ws = httpserver::create_webserver(8082);

   /ws.allow_ip("127.0.0.1");/

   file_response_resource fr;
   ws.register_resource("/download", &fr);
   ws.start(true);

2. set get request:http://localhost:8082/download

3. this is the debug process:
   
   *con_cls is null point
   4.the program is processing this method all the time and cant go into requests_answer_first_step

Expected behavior: [What you expect to happen]
the program can go into requests_answer_first_step
Actual behavior: [What actually happens]

Reproduces how often: [What percentage of the time does it reproduce?]
every time

Versions

• OS version (if on linux, the output of "uname -a")
• libhttpserver version (please specify whether compiled or packaged)
• libmicrohttpd version (please specify whether compiled or packaged)

If you have problems during build:

• Compiler version
• autotools version

Additional Information

Any additional information, configuration (especially build configuration flags if you compiled the libraries) or data that might be necessary to reproduce the issue.

If you have problems during build, please attach your config.log and the full scope of your error from make.

If you have problems at execution, please:

• attach the stacktrace in case of crash (a coredump would be even better).
• provide a main that reproduces the error.