TypeError: 'NoneType' object is not iterable when resume is used in thread.submit command

### Checked other resources

- [x] This is a bug, not a usage question. For questions, please use the LangChain Forum (https://forum.langchain.com/).
- [x] I added a clear and detailed title that summarizes the issue.
- [x] I read what a minimal reproducible example is (https://stackoverflow.com/help/minimal-reproducible-example).
- [x] I included a self-contained, minimal example that demonstrates the issue INCLUDING all the relevant imports. The code run AS IS to reproduce the issue.

### Example Code

```python
thread.submit(undefined, { command: { resume: [{"type": "accept"}] } });
```

### Error Message and Stack Trace (if applicable)

```shell
Traceback (most recent call last):
File "/Users/leopeng1995/workspaces/promptcn/deep-insight/.venv/lib/python3.12/site-packages/langgraph_api/worker.py", line 134, in wrap_user_errors
await consume(stream, run_id, resumable)
File "/Users/leopeng1995/workspaces/promptcn/deep-insight/.venv/lib/python3.12/site-packages/langgraph_api/stream.py", line 332, in consume
raise e
File "/Users/leopeng1995/workspaces/promptcn/deep-insight/.venv/lib/python3.12/site-packages/langgraph_api/stream.py", line 316, in consume
async for mode, payload in stream:
File "/Users/leopeng1995/workspaces/promptcn/deep-insight/.venv/lib/python3.12/site-packages/langgraph_api/stream.py", line 251, in astream_state
event = await wait_if_not_done(anext(stream, sentinel), done)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/leopeng1995/workspaces/promptcn/deep-insight/.venv/lib/python3.12/site-packages/langgraph_api/asyncio.py", line 91, in wait_if_not_done
raise e.exceptions[0] from None
File "/Users/leopeng1995/workspaces/promptcn/deep-insight/.venv/lib/python3.12/site-packages/langgraph/pregel/__init__.py", line 2768, in astream
async for _ in runner.atick(
File "/Users/leopeng1995/workspaces/promptcn/deep-insight/.venv/lib/python3.12/site-packages/langgraph/pregel/write.py", line 101, in _awrite
self.do_write(
File "/Users/leopeng1995/workspaces/promptcn/deep-insight/.venv/lib/python3.12/site-packages/langgraph/pregel/write.py", line 128, in do_write
write(_assemble_writes(writes))
^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/leopeng1995/workspaces/promptcn/deep-insight/.venv/lib/python3.12/site-packages/langgraph/pregel/write.py", line 183, in _assemble_writes
if ww := w.mapper(w.value):
^^^^^^^^^^^^^^^^^
File "/Users/leopeng1995/workspaces/promptcn/deep-insight/.venv/lib/python3.12/site-packages/langgraph/graph/state.py", line 1248, in _control_branch
for go in command.goto
^^^^^^^^^^^^
TypeError: 'NoneType' object is not iterable
During task with name '__start__' and id '17de729a-e0e0-aa69-dba1-583551ea7936'
```

### Description

The `update` and `goto` parameters for Command are optional. I'm passing a `resume` parameter in App.tsx, but why am I getting the following error when it crashes?

Command definition:

```
export interface Command {
/**
* An object to update the thread state with.
*/
update?: Record | [string, unknown][] | null;
/**
* The value to return from an `interrupt` function call.
*/
resume?: unknown;
/**
* Determine the next node to navigate to. Can be one of the following:
* - Name(s) of the node names to navigate to next.
* - `Send` command(s) to execute node(s) with provided input.
*/
goto?: Send | Send[] | string | string[];
}
```

App.tsx:

```
{thread.interrupt && (

human_in_the_loop.py:

```
from typing import Callable, TypedDict, Optional
from langchain_core.tools import BaseTool, tool as create_tool
from langchain_core.runnables import RunnableConfig
from langgraph.types import interrupt

class HumanInterruptConfig(TypedDict, total=False):
allow_accept: bool
allow_edit: bool
allow_respond: bool

class ActionRequest(TypedDict):
action: str
args: dict

class HumanInterrupt(TypedDict):
action_request: ActionRequest
config: HumanInterruptConfig
description: str

def add_human_in_the_loop(
tool: Callable | BaseTool,
*,
interrupt_config: Optional[HumanInterruptConfig] = None,
) -> BaseTool:
"""Wrap a tool to support human-in-the-loop review."""
if not isinstance(tool, BaseTool):
tool = create_tool(tool)

if interrupt_config is None:
interrupt_config = {
"allow_accept": True,
"allow_edit": True,
"allow_respond": True,
}

@create_tool(
tool.name,
description=tool.description,
args_schema=tool.args_schema
)
async def call_tool_with_interrupt(config: RunnableConfig, **tool_input):
request: HumanInterrupt = {
"action_request": {
"action": tool.name,
"args": tool_input
},
"config": interrupt_config,
"description": "Please review the tool call"
}
response = interrupt([request])[0]

if response["type"] == "accept":
tool_response = await tool.ainvoke(tool_input, config)
elif response["type"] == "edit":
tool_input = response["args"]["args"]
tool_response = await tool.ainvoke(tool_input, config)
elif response["type"] == "response":
user_feedback = response["args"]
tool_response = user_feedback
else:
raise ValueError(f"Unsupported interrupt response type: {response['type']}")

return tool_response

return call_tool_with_interrupt
```

### System Info

System Information
------------------
> OS: Darwin
> OS Version: Darwin Kernel Version 23.5.0: Wed May 1 20:19:05 PDT 2024; root:xnu-10063.121.3~5/RELEASE_ARM64_T8112
> Python Version: 3.12.8 (main, Jan 14 2025, 23:36:58) [Clang 19.1.6 ]

Package Information
-------------------
> langchain_core: 0.3.68
> langchain: 0.3.26
> langchain_community: 0.3.27
> langsmith: 0.3.45
> langchain_anthropic: 0.3.17
> langchain_dashscope: 0.1.8
> langchain_deepseek: 0.1.3
> langchain_google_genai: 2.1.8
> langchain_openai: 0.3.28
> langchain_tavily: 0.2.7
> langchain_text_splitters: 0.3.8
> langgraph_api: 0.2.94
> langgraph_cli: 0.3.4
> langgraph_license: Installed. No version info available.
> langgraph_runtime: Installed. No version info available.
> langgraph_runtime_inmem: 0.5.0
> langgraph_sdk: 0.1.73

Optional packages not installed
-------------------------------
> langserve

Other Dependencies
------------------
> aiohttp: 3.11.18
> aiohttp<4.0.0,>=3.8.3: Installed. No version info available.
> anthropic<1,>=0.57.0: Installed. No version info available.
> async-timeout<5.0.0,>=4.0.0;: Installed. No version info available.
> blockbuster<2.0.0,>=1.5.24: Installed. No version info available.
> click>=8.1.7: Installed. No version info available.
> cloudpickle>=3.0.0: Installed. No version info available.
> cryptography<45.0,>=42.0.0: Installed. No version info available.
> dashscope: 1.23.8
> dataclasses-json<0.7,>=0.5.7: Installed. No version info available.
> filetype: 1.2.0
> google-ai-generativelanguage: 0.6.18
> httpx: 0.28.1
> httpx-sse<1.0.0,>=0.4.0: Installed. No version info available.
> httpx>=0.25.0: Installed. No version info available.
> httpx>=0.25.2: Installed. No version info available.
> jsonpatch<2.0,>=1.33: Installed. No version info available.
> jsonschema-rs<0.30,>=0.20.0: Installed. No version info available.
> langchain-anthropic;: Installed. No version info available.
> langchain-aws;: Installed. No version info available.
> langchain-azure-ai;: Installed. No version info available.
> langchain-cohere;: Installed. No version info available.
> langchain-community;: Installed. No version info available.
> langchain-core<1.0.0,>=0.3.47: Installed. No version info available.
> langchain-core<1.0.0,>=0.3.51: Installed. No version info available.
> langchain-core<1.0.0,>=0.3.66: Installed. No version info available.
> langchain-core<1.0.0,>=0.3.68: Installed. No version info available.
> langchain-core>=0.3.64: Installed. No version info available.
> langchain-deepseek;: Installed. No version info available.
> langchain-fireworks;: Installed. No version info available.
> langchain-google-genai;: Installed. No version info available.
> langchain-google-vertexai;: Installed. No version info available.
> langchain-groq;: Installed. No version info available.
> langchain-huggingface;: Installed. No version info available.
> langchain-mistralai;: Installed. No version info available.
> langchain-ollama;: Installed. No version info available.
> langchain-openai;: Installed. No version info available.
> langchain-openai<1.0.0,>=0.3.9: Installed. No version info available.
> langchain-perplexity;: Installed. No version info available.
> langchain-text-splitters<1.0.0,>=0.3.8: Installed. No version info available.
> langchain-together;: Installed. No version info available.
> langchain-xai;: Installed. No version info available.
> langchain<1.0.0,>=0.3.26: Installed. No version info available.
> langgraph-api<0.3.0,>=0.2.67;: Installed. No version info available.
> langgraph-checkpoint>=2.0.23: Installed. No version info available.
> langgraph-checkpoint>=2.0.25: Installed. No version info available.
> langgraph-runtime-inmem<0.4.0,>=0.3.0;: Installed. No version info available.
> langgraph-runtime-inmem<0.6,>=0.5.0: Installed. No version info available.
> langgraph-sdk>=0.1.0;: Installed. No version info available.
> langgraph-sdk>=0.1.71: Installed. No version info available.
> langgraph>=0.2: Installed. No version info available.
> langgraph>=0.3.27: Installed. No version info available.
> langsmith-pyo3: Installed. No version info available.
> langsmith>=0.1.125: Installed. No version info available.
> langsmith>=0.1.17: Installed. No version info available.
> langsmith>=0.3.45: Installed. No version info available.
> numpy>=1.26.2;: Installed. No version info available.
> numpy>=2.1.0;: Installed. No version info available.
> openai-agents: Installed. No version info available.
> openai<2.0.0,>=1.86.0: Installed. No version info available.
> opentelemetry-api: 1.32.1
> opentelemetry-exporter-otlp-proto-http: Installed. No version info available.
> opentelemetry-sdk: 1.32.1
> orjson: 3.10.12
> orjson>=3.10.1: Installed. No version info available.
> orjson>=3.9.7: Installed. No version info available.
> packaging: 24.2
> packaging<25,>=23.2: Installed. No version info available.
> pydantic: 2.11.7
> pydantic-settings<3.0.0,>=2.4.0: Installed. No version info available.
> pydantic<3.0.0,>=2.7.4: Installed. No version info available.
> pydantic>=2.7.4: Installed. No version info available.
> pyjwt>=2.9.0: Installed. No version info available.
> pytest: Installed. No version info available.
> python-dotenv>=0.8.0;: Installed. No version info available.
> PyYAML>=5.3: Installed. No version info available.
> requests: 2.32.3
> requests-toolbelt: 1.0.0
> requests<3,>=2: Installed. No version info available.
> rich: 14.0.0
> SQLAlchemy<3,>=1.4: Installed. No version info available.
> sse-starlette<2.2.0,>=2.1.0: Installed. No version info available.
> sse-starlette>=2: Installed. No version info available.
> starlette>=0.37: Installed. No version info available.
> starlette>=0.38.6: Installed. No version info available.
> structlog<26,>=24.1.0: Installed. No version info available.
> structlog>23: Installed. No version info available.
> tenacity!=8.4.0,<10,>=8.1.0: Installed. No version info available.
> tenacity!=8.4.0,<10.0.0,>=8.1.0: Installed. No version info available.
> tenacity>=8.0.0: Installed. No version info available.
> tiktoken: 0.7.0
> tiktoken<1,>=0.7: Installed. No version info available.
> truststore>=0.1: Installed. No version info available.
> typing-extensions>=4.7: Installed. No version info available.
> uvicorn>=0.26.0: Installed. No version info available.
> watchfiles>=0.13: Installed. No version info available.
> zstandard: 0.23.0

Start with langgraph/graph/state.py at _control_branch and langgraph/pregel/write.py at _assemble_writes, then run the shown TypeScript thread.submit call with the Python human_in_the_loop.py wrapper. Done means the resume-only command no longer raises the reported TypeError and the behavior is covered by a regression test.

Written by the indexing model from the issue text.