fix model args

vit_gpt2/modeling_flax_vit_gpt2_lm.py

@@ -512,8 +512,8 @@ class FlaxViTGPT2LMForConditionalGeneration(FlaxViTGPT2LMPreTrainedModel):
         for key in text_kwargs.keys():
             del kwargs["text_" + key]
 
-        vision_model_args = vision_kwargs.pop('model_args', None)
-        text_model_args = text_kwargs.pop('model_args', None)
+        vision_model_args = vision_kwargs.pop('model_args', [])
+        text_model_args = text_kwargs.pop('model_args', [])
 
         # Load and initialize the vit & gpt2 model
         vision_model = vision_kwargs.pop("model", None)