User-agent no longer present on log pages if supplied user-agent is null

[msherry]

Like https://dp.balancedpayments.com/#/marketplaces/MP2AjEDjo7VjVsx0EfJijV8b/logs/OHM31b59bfa906b11e49dde06429171ffad . It would be great to have this restored, since displaying 'null' is still valuable info.

[kyungmin]

@msherry The User-Agent was not captured for some reason.

         "headers": {
            "X-Real-Ip": "xxx",
            "X-Forwarded-For": "xxx",
            "User-Agent": null
          },

[kyungmin]

Oh, I see what you mean.