Debugging and removing redundant lines

I think these changes are needed and fixes a bug but I don't know what testing process was done.
Please see [this issue](https://huggingface.co/baidu/ERNIE-4.5-VL-28B-A3B-PT/discussions/7#68a699b08258e261e1f1042f) and if deemed valid, I will move the explanations here.

modeling_ernie4_5_vl.py

@@ -2882,11 +2882,6 @@ class Ernie4_5_Model(Ernie4_5_PretrainedModel):
         if past_key_values is None:
             past_key_values = tuple([None] * len(self.layers))
 
-        seq_length_with_past = seq_length
-        cache_length = 0
-        if past_key_values[0] is not None:
-            cache_length = past_key_values[0][0].shape[1]
-            seq_length_with_past += cache_length
         if inputs_embeds is None:
             inputs_embeds = self.embed_tokens(input_ids)
 
@@ -2908,9 +2903,7 @@ class Ernie4_5_Model(Ernie4_5_PretrainedModel):
             if output_hidden_states:
                 all_hidden_states += (hidden_states,)
 
-            past_key_value = (
-                past_key_values[idx] if past_key_values is not None else None
-            )
+            past_key_value = past_key_values[idx]
             layer_outputs = decoder_layer(
                 hidden_states,
                 attention_mask,