[misc] Revert # 12833 (#12857)

Signed-off-by: <>
Co-authored-by: EC2 Default User <[email protected]>

Author: khluu

vllm/inputs/preprocess.py

@@ -260,6 +260,9 @@ def _process_multimodal(
         mm_processor = self.mm_registry.create_processor(
             self.model_config, tokenizer)
 
+        if isinstance(prompt, list):
+            prompt = tokenizer.decode(prompt)
+
         if mm_processor_kwargs is None:
             mm_processor_kwargs = {}