[Bugfix] Allow skipping MoE in NVFP4 (fix for MTP) (#25987)

Signed-off-by: Benjamin Chislett <bchislett@nvidia.com>

vllm/model_executor/layers/fused_moe/layer.py

@@ -1194,6 +1194,8 @@ class FusedMoE(CustomOp):
             if quant_config is None
             else quant_config.get_quant_method(self, prefix)
         )
+        if quant_method is None:
+            quant_method = UnquantizedFusedMoEMethod(moe)
 
         assert quant_method is not None
         assert isinstance(quant_method, FusedMoEMethodBase)