Fixed error 500 if the user does not have notification username

boards/abstracts/settingsmanager.py

@@ -145,10 +145,12 b' class SettingsManager:'
 
     def get_notification_usernames(self):
         names = set()
-        name_list = self.get_setting(SETTING_USERNAME).strip()
-        if name_list is not None and len(name_list) > 0:
-            names = name_list.lower().split(',')
-            names = set(name.strip() for name in names)
+        name_list = self.get_setting(SETTING_USERNAME)
+        if name_list is not None:
+            name_list = name_list.strip()
+            if len(name_list) > 0:
+                names = name_list.lower().split(',')
+                names = set(name.strip() for name in names)
         return names