fixed crash when no content-type
to replicate just make a request like this, and it will crash
curl -v https://example.com/xxx -d '1' -H 'Content-Type:'
coverage: 94.311%. remained the same
when pulling 1274e7653cd1d8b4c6aadd62786188621ed37b7b on colinshr:master
into fbee074bef0c0995aeb54575bdab0b2e2d9d4e72 on richardgirges:master.
fixed crash when no content-type to replicate just make a request like this, and it will crash curl -v https://example.com/xxx -d '1' -H 'Content-Type:'