Prevent a basic hack.

src/storage.cr

@@ -133,6 +133,8 @@ class DNSManager::Storage
 		end
 
 		matching_domains.each do |md|
+			# Prevent empty domains (from crafted requests) to be accepted.
+			return Response::InvalidDomainName.new unless (domain.chomp md).size > 2
 			Baguette::Log.info "Add new domain #{domain} (matching domain #{md})"
 		end