Fix clock item reset.

src/models.py

@@ -362,10 +362,16 @@ class ClockInfo(db.Model):
         self.log_source = source_number
         if current_playlist:
             self.current_playlist = json.dumps(current_playlist.to_dict(), default=str)
+        else:
+            self.current_playlist = None
         if current_schedule:
             self.current_schedule = json.dumps(current_schedule.to_dict(), default=str)
+        else:
+            self.current_schedule = None            
         if next_schedule:
             self.next_schedule = json.dumps(next_schedule.to_dict(), default=str)
+        else:
+            self.next_schedule = None
 
 
     @staticmethod