ad-connector: fix all users revoked when AD is down

Fix f037a08d didn't work for active directory since
UserProfileService.getUserProfile returns an empty array instead of null
for Active Directory. In this case we must also check for an empty array
in order to identify that the AD server is down.

Ticket: https://redmine.savoirfairelinux.com/issues/7656
Change-Id: Icda219ec5f85b5b40e7a0c56957b2eb1dcd4f866

ad-connector/src/main/java/net/jami/jams/ad/connector/service/UserProfileService.java

@@ -203,7 +203,7 @@ public class UserProfileService {
         List<UserProfile> profilesFromAD =
                 getUserProfile("*", "LOGON_NAME", false, Optional.empty());
         // Do not revoke users if there is an error, the AD server could be down.
-        if (profilesFromAD != null) {
+        if (profilesFromAD != null && !profilesFromAD.isEmpty()) {
             // There is a use case where a user is not in the AD server but is in the database.
             // When this happens, we need to revoke the user from the database.
             List<UserProfile> profilesFromDatabase =