Fix UnboundLocalError: multitalk_audio_stride referenced before assignment in WanVideoSampler

[kylinjg]

Problem

WanVideoSampler raises an UnboundLocalError on any run that does not pass multitalk_embeds (i.e. the large majority of workflows — standard T2V/I2V, VACE, Fun-Control, etc.):

UnboundLocalError: cannot access local variable 'multitalk_audio_stride' where it is not associated with a value
  File "custom_nodes/ComfyUI-WanVideoWrapper/nodes_sampler.py", line 822, in process
    if multitalk_audio_stride is not None:

Root cause

multitalk_audio_stride is only bound inside the if multitalk_embeds is not None: branch:

multitalk_audio_stride = multitalk_embeds.get("audio_stride", None)

but it is later read unconditionally:

if multitalk_audio_stride is not None:
    audio_stride = multitalk_audio_stride

When multitalk_embeds is None, the name is never assigned, so the later read throws.

Fix

Initialize multitalk_audio_stride = None alongside the other MultiTalk locals (multitalk_audio_embeds, audio_emb_slice, audio_features_in), so the unconditional read is always safe. One line, no behavior change for the MultiTalk path.

Reproduction

Run any VACE / T2V / I2V workflow through WanVideoSampler without a MultiTalk embed connected → error before this patch, works after.