[BugFix] Fix min_tokens when eos_token_id is None (#4389)

Co-authored-by: DefTruth <31974251+deftruth@users.noreply.github.com>

vllm/engine/llm_engine.py

@@ -431,9 +431,10 @@ class LLMEngine:
         # Defensive copy of SamplingParams, which are used by the sampler,
         # this doesn't deep-copy LogitsProcessor objects
         sampling_params = sampling_params.clone()
-        # inject the eos token id into the sampling_params to support min_tokens
+        # Add the eos token id into the sampling_params to support min_tokens
         # processing
-        sampling_params.eos_token_id = seq.eos_token_id
+        if seq.eos_token_id is not None:
+            sampling_params.all_stop_token_ids.add(seq.eos_token_id)
         sampling_params.update_from_generation_config(
             self.generation_config_fields)