user_data drops null values that are passed in

[DoctorEvil92]

Hi, it seems like user_data will drop dict keys that have null values under them. See the example

from crawlee.router import Router
from crawlee.crawlers import BeautifulSoupCrawler, BeautifulSoupCrawlingContext
from crawlee import Request
import asyncio


async def main():
    # define links
    target_url = "https://example.com/" # target site

    # define router
    router = Router[BeautifulSoupCrawlingContext]()
    @router.handler("MAIN")
    async def main_handler(context : BeautifulSoupCrawlingContext) -> None:
        loaded_user_data = dict(context.request.user_data)
        print("loaded user_data:", loaded_user_data)
        return
    
    # then try to do a request with crawlee with the same proxy
    crawler = BeautifulSoupCrawler(request_handler=router)

    # run it
    await crawler.run( [Request.from_url(target_url, label='MAIN', user_data={"a":1, "b":"2", "c":None, "d":False})] )

    
    

if __name__ == '__main__':
    asyncio.run(main())

"c" key got dropped as I load it into a dictionary in the handler.