Errors caused by empty HTTP headers

[aw]

This was discovered thanks to Amazon S3 sending an invalid HTTP Content-Type header, which in fact is not even allowed to be empty according to the RFCs.

Location: https://s3.amazonaws.com/production.s3.rubygems.org/specs.4.8.gz

HTTP/1.1 200 OK
x-amz-id-2: alURqgFXa/nVfPpLEJQVOs3fJ8t9C9Z+MlAdMAaC62d1ZsccK06NVpqRLxlD1KVB
x-amz-request-id: 1581E6BF3225E185
Date: Wed, 29 Apr 2015 15:22:57 GMT
x-amz-version-id: qc5dRNqFJO68y1JxMODSS1fQf.8WZ8IF
Last-Modified: Wed, 29 Apr 2015 15:21:33 GMT
ETag: "c64eff68233a552b9737972ad8c2fb86"
Accept-Ranges: bytes
Content-Type: 
Content-Length: 2364063
Server: AmazonS3

I vote 👍 to just drop empty headers.