avoid crash when response has no attachments

[erikdw]

Description

Symptoms

I noticed llm chat was crashing a ... lot.

Tracebacks looked like this:

Traceback (most recent call last):
  File "/opt/homebrew/bin/llm", line 8, in <module>
    sys.exit(cli())
             ~~~^^
  File "/opt/homebrew/Cellar/llm/0.17/libexec/lib/python3.13/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
           ~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/llm/0.17/libexec/lib/python3.13/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/opt/homebrew/Cellar/llm/0.17/libexec/lib/python3.13/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
                           ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/opt/homebrew/Cellar/llm/0.17/libexec/lib/python3.13/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/llm/0.17/libexec/lib/python3.13/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/opt/homebrew/Cellar/llm/0.17/libexec/lib/python3.13/site-packages/llm/cli.py", line 535, in chat
    for chunk in response:
                 ^^^^^^^^
  File "/opt/homebrew/Cellar/llm/0.17/libexec/lib/python3.13/site-packages/llm/models.py", line 169, in __iter__
    for chunk in self.model.execute(
                 ~~~~~~~~~~~~~~~~~~^
        self.prompt,
        ^^^^^^^^^^^^
    ...<2 lines>...
        conversation=self.conversation,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ):
    ^
  File "/opt/homebrew/Cellar/llm/0.17/libexec/lib/python3.13/site-packages/llm/default_plugins/openai_models.py", line 315, in execute
    if prev_response.attachments:
       ^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Response' object has no attribute 'attachments'

Problem

The python code is not checking if there is an attachments attribute before accessing it.

Introduction of Issue

Came in this change: #590

Solution

Check for existence of attachments attribute before accessing.

Testing

Made the change to my local version of the code in my homebrew install path, and the crashes went away.

[simonw]

Thanks for this - I landed a fix already in:

• llm chat errors on followup since 0.6 #601