[CI] Fix Nemotron nightly mixed precision checkpoints test (#27284)

Co-authored-by: Brayden Zhong <brayden.zhong@radixark.ai>

python/sglang/srt/model_executor/model_runner.py

@@ -1419,14 +1419,16 @@ class ModelRunner(ModelRunnerKVCacheMixin):
         )
 
         # TODO: Make sure all models have `quant_config` attribute, and all online quantization methods register which layers they actually quantize.
+        # TODO: Move this online-quantization reporting out of ModelRunner.
+        quantized_layers = getattr(
+            getattr(self.model, "quant_config", None), "quantized_layers", None
+        )
         if (
-            hasattr(self.model, "quant_config")
-            and hasattr(self.model.quant_config, "quantized_layers")
-            and self.server_args.quantization is not None
+            self.server_args.quantization is not None
+            and isinstance(quantized_layers, tuple)
+            and len(quantized_layers) == 2
         ):
-            layer_types, quantized_layers_count = (
-                self.model.quant_config.quantized_layers
-            )
+            layer_types, quantized_layers_count = quantized_layers
             logger.info(
                 f"Online {self.server_args.quantization} quantization: quantized {quantized_layers_count} layers of types: {layer_types}"
             )