fix condition

Signed-off-by: Dipika Sikka <dipikasikka1@gmail.com>

Author: dsikka

vllm/config.py

@@ -3178,7 +3178,8 @@ def _verify_args(self) -> Self:
         from vllm.transformers_utils.configs import SpeculatorsConfig
 
         eagle3_target_supported = ["llama"]
-        if isinstance(self.draft_model_config.hf_config, SpeculatorsConfig):
+        if self.draft_model_config and isinstance(
+                self.draft_model_config.hf_config, SpeculatorsConfig):
             eagle3_target_supported.append("qwen")
 
         if self.method == "eagle3" and self.target_model_config and not any(