If FuturesDict callback has been GCed, don't call it

libs/checkpoint-postgres/uv.lock

@@ -308,7 +308,7 @@ wheels = [
 
 [[package]]
 name = "langgraph-checkpoint"
-version = "2.0.26"
+version = "2.1.0"
 source = { editable = "../checkpoint" }
 dependencies = [
     { name = "langchain-core" },

libs/checkpoint-sqlite/uv.lock

@@ -320,7 +320,7 @@ wheels = [
 
 [[package]]
 name = "langgraph-checkpoint"
-version = "2.0.26"
+version = "2.1.0"
 source = { editable = "../checkpoint" }
 dependencies = [
     { name = "langchain-core" },

libs/langgraph/langgraph/pregel/runner.py

@@ -104,7 +104,8 @@ class FuturesDict(Generic[F, E], dict[F, Optional[PregelExecutableTask]]):
         fut: F,
     ) -> None:
         try:
-            self.callback()(task, _exception(fut))  # type: ignore[misc]
+            if cb := self.callback():
+                cb(task, _exception(fut))
         finally:
             with self.lock:
                 self.done.add(fut)

libs/prebuilt/uv.lock

@@ -320,7 +320,7 @@ wheels = [
 
 [[package]]
 name = "langgraph"
-version = "0.5.0rc0"
+version = "0.5.0rc1"
 source = { editable = "../langgraph" }
 dependencies = [
     { name = "langchain-core" },