What

During Krea-2 image generation, a crash occurs in do_controlnet_step because the controlnet path passes incorrect arguments to the model forward callback. The original code attempts to modify sample_model_input but never actually calls the model forward, and the callback signature is inconsistent. This leads to a TypeError and crash.

Fix

• Added a None-check on control_data to avoid iterating over None.
• Built cross_attention_kwargs containing the controlnet residuals and conditioning settings.
• Call model_forward_callback with the correct arguments, including a fallback for callbacks that don't accept cross_attention_kwargs.
• Return the updated sample from the method.

This ensures ControlNet steps work for models like Krea-2 that expect the proper conditioning format.

Closes #9444