Update heatmaps solution (#16720)

Co-authored-by: UltralyticsAssistant <web@ultralytics.com>

ultralytics/solutions/solutions.py

@@ -57,7 +57,8 @@ class BaseSolution:
             self.clss = self.track_data.cls.cpu().tolist()
             self.track_ids = self.track_data.id.int().cpu().tolist()
         else:
-            LOGGER.warning("WARNING ⚠️ tracks none, no keypoints will be considered.")
+            LOGGER.warning("WARNING ⚠️ no tracks found!")
+            self.boxes, self.clss, self.track_ids = [], [], []
 
     def store_tracking_history(self, track_id, box):
         """