fix: Avoid error getting translated content for unsaved or deleted bl…

…ocks in __str__ method

backend/experiment/models.py

@@ -227,8 +227,15 @@ class Block(models.Model):
     theme_config = models.ForeignKey(ThemeConfig, on_delete=models.SET_NULL, blank=True, null=True)
 
     def __str__(self):
-        content = self.get_fallback_content()
-        return content.name if content and content.name else self.slug
+        # If this block is unsaved or being deleted (has no PK),
+        # avoid calling get_fallback_content() (which does a DB query).
+        if not self.pk:
+            # Provide a fallback label or just return self.slug if present.
+            return self.slug or "Deleted Block"
+
+    # change message
+    def save(self, *args, **kwargs):
+        super().save(*args, **kwargs)
 
     @property
     def name(self):
@@ -450,10 +457,6 @@ def get_fallback_content(self) -> "BlockTranslatedContent | None":
             Fallback content
         """
 
-        # If the block is not saved yet or is being deleted, there is no fallback content
-        if not self.pk:
-            return None
-
         if not self.phase or self.phase.experiment:
             return self.translated_contents.first()