add optional chaining for http.defaults.host in contentstackClient

Author: harshithad0703

lib/contentstackClient.js

@@ -31,7 +31,7 @@ export default function contentstackClient ({ http }) {
 
   if (region && region !== Region.NA) {
     baseUrlPath = `https://${region}-api.contentstack.com:443/v3/user-session`
-  } else if (!region && http.defaults.host) {
+  } else if (!region && http?.defaults?.host) {
     baseUrlPath = `https://${http.defaults.host}:443/v3/user-session`
   } else {
     baseUrlPath = `https://api.contentstack.io:443/v3/user-session`