Add assertion for vision_use_head in Gemma3VLBridge unit tests

Signed-off-by: Ao Tang <aot@nvidia.com>

Author: suiyoubi

tests/unit_tests/models/gemma_vl/test_gemma3_vl_bridge.py

@@ -166,6 +166,7 @@ def test_provider_bridge_vl_specific_config(self, gemma3_vl_bridge, mock_hf_pret
 
         # Check vision config
         assert isinstance(provider.vision_config, SiglipVisionConfig)
+        assert provider.vision_config.vision_use_head is False
         assert provider.mm_tokens_per_image == 256
 
     def test_provider_bridge_vision_projector_config(self, gemma3_vl_bridge, mock_hf_pretrained):