fix: DIA-1419: RunTime error occurs on trying to delete certain promp…

…ts (#6374)

Co-authored-by: nik <nik@heartex.net>

label_studio/tasks/models.py

@@ -1291,9 +1291,23 @@ def remove_predictions_from_project(sender, instance, **kwargs):
     """Remove predictions counters"""
     instance.task.total_predictions = instance.task.predictions.all().count() - 1
     instance.task.save(update_fields=['total_predictions'])
+
+    # if there is PredictionMeta object associated with the Prediction object, delete it
+    if hasattr(instance, 'meta'):
+        logger.debug(f'Deleting PredictionMeta object associated with Prediction object {instance.id}')
+        instance.meta.delete()
+
     logger.debug(f'Updated total_predictions for {instance.task.id}.')
 
 
+@receiver(pre_delete, sender=FailedPrediction)
+def remove_failed_predictions_from_project(sender, instance, **kwargs):
+    # if there is PredictionMeta object associated with the Prediction object, delete it
+    if hasattr(instance, 'meta'):
+        logger.debug(f'Deleting PredictionMeta object associated with Prediction object {instance.id}')
+        instance.meta.delete()
+
+
 @receiver(post_save, sender=Prediction)
 def save_predictions_to_project(sender, instance, **kwargs):
     """Add predictions counters"""