[Bugfix] fix moe marlin `topk_weight` loading (#18080)

Co-authored-by: mgoin <mgoin64@gmail.com>

csrc/moe/marlin_moe_wna16/marlin_template.h

@@ -473,15 +473,15 @@ __global__ void Marlin(
       if (mul_topk_weights) {
   #pragma unroll
         for (int i = 0; i < 4; i++) {
+          int idx = tid4 * 4 + i;
+          idx = idx < block_num_valid_tokens ? idx : 0;
           if constexpr (w_type == vllm::kFE2M1f) {
-            sh_block_topk_weights[tid4 * 4 + i] = __hmul2(
-                global_scale,
-                Dtype::num2num2(Dtype::float2num(
-                    topk_weights_ptr[sh_block_sorted_ids[tid4 * 4 + i]])));
+            sh_block_topk_weights[idx] = __hmul2(
+                global_scale, Dtype::num2num2(Dtype::float2num(
+                                  topk_weights_ptr[sh_block_sorted_ids[idx]])));
           } else {
-            sh_block_topk_weights[tid4 * 4 + i] =
-                Dtype::num2num2(Dtype::float2num(
-                    topk_weights_ptr[sh_block_sorted_ids[tid4 * 4 + i]]));
+            sh_block_topk_weights[idx] = Dtype::num2num2(
+                Dtype::float2num(topk_weights_ptr[sh_block_sorted_ids[idx]]));
           }
         }
       }