fix a bug for gpu version

source/sample/transformer/T2TSearch.cpp

@@ -354,6 +354,7 @@ void T2TSearch::Generate(T2TStateBundle* beam)
     probPath.Reshape(probPath.unitNum, 1);
     indexCPU.Reshape(indexCPU.GetDim(0), indexCPU.GetDim(-1));
 
+    indexCPU.SetDevice(prob.devID);
     probTopK = Gather(prob, indexCPU);
     probPathTopK = Gather(probPath, indexCPU);