Fix retrieving multiple certificate fingerprints on InspIRCd v4. (#379)

* Fix retrieving multiple certificate fingerprints on InspIRCd v4.

* Update to match my suggestion after review.

Author: SadieCat

src/commands/handlers/user.js

@@ -272,7 +272,10 @@ const handlers = {
     RPL_WHOISCERTFP: function(command, handler) {
         const cache_key = command.params[1].toLowerCase();
         const cache = handler.cache('whois.' + cache_key);
-        cache.certfp = command.params[command.params.length - 1];
+        const certfp = command.params[command.params.length - 1];
+        cache.certfp = cache.certfp || certfp;
+        cache.certfps = cache.certfps || [];
+        cache.certfps.push(certfp);
     },
 
     RPL_WHOISACCOUNT: function(command, handler) {