FIX: Prevent TypeError: NoneType on model switching in token counter

This fixes the critical `TypeError: argument of type 'NoneType' is not iterable` that frequently occurs in the token counter when the main Stable Diffusion model is being unloaded or reloaded (e.g., during XYZ Plot or manual model switching).

The error happens because the `get_token_counter` function tries to access `sd_models.model_data.sd_model.cond_stage_model` when `sd_model` is momentarily `None`.

The fix adds a robust check for `sd_models.model_data.sd_model is None` at the start of the function, ensuring the token counter safely returns 0 instead of causing an ASGI application crash across all environments (A1111, Forge/reForge).

scripts/physton_prompt/get_token_counter.py

@@ -1,7 +1,7 @@
 from modules import script_callbacks, extra_networks, prompt_parser, sd_models
 from modules.sd_hijack import model_hijack
 from functools import partial, reduce
- 
+
 
 def get_token_counter(text, steps):
     # Check if the model is fully loaded to prevent TypeError during model switching