Fix check whether instance was found (it may be falsey if empty instance list)

client/ayon_core/plugins/publish/integrate_attach_reviewable.py

@@ -57,7 +57,7 @@ class AttachReviewables(
                 ),
                 None,
             )
-            if not attach_instance:
+            if attach_instance is None:
                 continue
 
             # Skip inactive instances