Fix undefined method error

[FixRM rapid7#8330]

Author: wchen-r7

modules/auxiliary/scanner/http/sevone_enum.rb

@@ -86,6 +86,11 @@ def do_login(user, pass)
 				}
 			})
 
+		if res.nil?
+			print_error("Connection timed out")
+			return :abort
+		end
+
 		check_key = "The user has logged in successfully."
 
 		key = JSON.parse(res.body)["statusString"]