Makes sure that the script fails if the HTTP request did. Closes #1046

CHANGELOG

@@ -1,5 +1,8 @@
 #s wa Nmap Changelog ($Id$); -*-text-*-
 
+o [NSE][GH#1046] Script http-headers now fails properly if the target does not
+  return a valid HTTP response. [spacewander]
+
 o [NSE] rsa-vuln-roca checks for RSA keys generated by Infineon TPMs vulnerable
   to Return Of Coppersmith Attack (ROCA) (CVE-2017-15361). Checks SSH and TLS
   services. [Daniel Miller]

scripts/http-headers.nse

@@ -57,14 +57,10 @@ action = function(host, port)
     request_type = "GET"
   end
 
-  if(result == nil) then
+  if not (result and result.status) then
     return fail("Header request failed")
   end
 
-  if(result.rawheader == nil) then
-    return fail("Header request didn't return a proper header")
-  end
-
   table.insert(result.rawheader, "(Request type: " .. request_type .. ")")
 
   return stdnse.format_output(true, result.rawheader)