fix do fission when UnsegmentSum's input0 shape size is 1

mindspore/ccsrc/backend/optimizer/ascend/ir_fission/unsorted_segment_sum_fission.cc

@@ -94,6 +94,10 @@ const AnfNodePtr UnsortSegmentSumFission::Process(const FuncGraphPtr &graph, con
     return nullptr;
   }
   auto input0_shape = AnfAlgo::GetPrevNodeOutputInferShape(origin_node, 0);
+  if (input0_shape.size() < 2) {
+    MS_LOG(INFO) << "Input0's shape size less than 2, not optimize";
+    return nullptr;
+  }
   if (input0_shape[input0_shape.size() - 1] != 1) {
     MS_LOG(INFO) << "UnsortedSegmentSum is not need fission. The last value of input0's shape is "
                  << input0_shape[input0_shape.size() - 1];