update num_expert_group

vllm/model_executor/layers/fused_moe/layer.py

@@ -1203,6 +1203,7 @@ class FusedMoE(CustomOp):
         # moe_fused_gate kernel ensure that num_experts/num_expert_group does not exceed MAX_VPT=32 now. And when kernel can handle MAX_VPT > 32, we can remove this assertion.
         self.use_fused_gate = envs.VLLM_ENABLE_MOE_FUSED_GATE \
             and self.e_score_correction_bias is not None \
+                 and num_expert_group is not None \
                     and self.global_num_experts // num_expert_group <= 32 \
                         and is_power_of_two(e_score_correction_bias.shape[0])