fix: handle missing blob attribute in shallow checkpoint savers (#80)

Add defensive checks in AsyncShallowRedisSaver and ShallowRedisSaver
to filter out documents with None or missing blob attributes when
loading pending sends. This prevents AttributeError when querying
checkpoint writes from the TASKS channel.

Fixes #80

Author: bsbodden

langgraph/checkpoint/redis/ashallow.py

@@ -646,12 +646,11 @@ async def _aload_pending_sends(
 
         # Extract type and blob pairs
         # Handle both direct attribute access and JSON path access
+        # Filter out documents where blob is None (similar to AsyncRedisSaver in aio.py)
         return [
-            (
-                getattr(doc, "type", ""),
-                getattr(doc, "$.blob", getattr(doc, "blob", b"")),
-            )
+            (getattr(doc, "type", ""), blob)
             for doc in sorted_writes
+            if (blob := getattr(doc, "$.blob", getattr(doc, "blob", None))) is not None
         ]
 
     async def _aload_pending_writes(

langgraph/checkpoint/redis/shallow.py

@@ -675,12 +675,11 @@ def _load_pending_sends(
 
         # Extract type and blob pairs
         # Handle both direct attribute access and JSON path access
+        # Filter out documents where blob is None (similar to RedisSaver in __init__.py)
         return [
-            (
-                getattr(doc, "type", ""),
-                getattr(doc, "$.blob", getattr(doc, "blob", b"")),
-            )
+            (getattr(doc, "type", ""), blob)
             for doc in sorted_writes
+            if (blob := getattr(doc, "$.blob", getattr(doc, "blob", None))) is not None
         ]
 
     def _make_shallow_redis_checkpoint_key_cached(