fix: checkpoint save issue in advanced dreambooth lora sdxl script (#8926)

Co-authored-by: Linoy Tsaban <57615435+linoytsaban@users.noreply.github.com>

Author: akbaig

examples/advanced_diffusion_training/train_dreambooth_lora_sdxl_advanced.py

@@ -1605,13 +1605,15 @@ def save_model_hook(models, weights, output_dir):
                 if isinstance(model, type(unwrap_model(unet))):
                     unet_lora_layers_to_save = convert_state_dict_to_diffusers(get_peft_model_state_dict(model))
                 elif isinstance(model, type(unwrap_model(text_encoder_one))):
-                    text_encoder_one_lora_layers_to_save = convert_state_dict_to_diffusers(
-                        get_peft_model_state_dict(model)
-                    )
+                    if args.train_text_encoder:
+                        text_encoder_one_lora_layers_to_save = convert_state_dict_to_diffusers(
+                            get_peft_model_state_dict(model)
+                        )
                 elif isinstance(model, type(unwrap_model(text_encoder_two))):
-                    text_encoder_two_lora_layers_to_save = convert_state_dict_to_diffusers(
-                        get_peft_model_state_dict(model)
-                    )
+                    if args.train_text_encoder:
+                        text_encoder_two_lora_layers_to_save = convert_state_dict_to_diffusers(
+                            get_peft_model_state_dict(model)
+                        )
                 else:
                     raise ValueError(f"unexpected save model: {model.__class__}")