Metadata status changes notification mails improvements:

- Don't add saludation if the user to notify is the catalogue administrator (defined in settings), as only has the email address.
- Filter out the users without mail when retrieving the users to notify

core/src/main/java/org/fao/geonet/kernel/metadata/DefaultStatusActions.java

@@ -48,6 +48,8 @@
 import org.springframework.context.ApplicationContext;
 
 import java.util.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import static org.fao.geonet.kernel.setting.Settings.SYSTEM_FEEDBACK_EMAIL;
 import static org.fao.geonet.util.LocalizedEmailComponent.ComponentType.*;
@@ -330,22 +332,24 @@ protected void notify(List<User> userToNotify, MetadataStatus status) throws Exc
             );
         }
 
-        LocalizedEmail localizedEmail = new LocalizedEmail(false);
-        localizedEmail.addComponents(emailSubjectComponent, emailMessageComponent, emailSalutationComponent);
-
-        String subject = localizedEmail.getParsedSubject(feedbackLocales);
-
         for (User user : userToNotify) {
+            LocalizedEmail localizedEmail = new LocalizedEmail(false);
+
             String userName = Joiner.on(" ").skipNulls().join(user.getName(), user.getSurname());
             //If we have a userName add the salutation
             String message;
             if (StringUtils.isEmpty(userName)) {
+                localizedEmail.addComponents(emailSubjectComponent, emailMessageComponent);
+
                 message = localizedEmail.getParsedMessage(feedbackLocales);
             } else {
+                localizedEmail.addComponents(emailSubjectComponent, emailMessageComponent, emailSalutationComponent);
+
                 Map<String, String> replacements = new HashMap<>();
                 replacements.put("{{userName}}", userName);
                 message = localizedEmail.getParsedMessage(feedbackLocales, replacements);
             }
+            String subject = localizedEmail.getParsedSubject(feedbackLocales);
             sendEmail(user.getEmail(), subject, message);
         }
     }
@@ -449,7 +453,9 @@ public static List<User> getUserToNotify(StatusValueNotificationLevel notificati
                 }
             }
         }
-        return users;
+
+        // Filter out users without email
+        return users.stream().filter(u -> StringUtils.isNotEmpty(u.getEmail())).collect(Collectors.toList());
     }
 
     public static List<Group> getGroupToNotify(StatusValueNotificationLevel notificationLevel, List<String> groupNames) {