clean a little bit code.

paddle/function/ContextProjectionOp.cpp

@@ -232,7 +232,7 @@ public:
     /// input grad and output grad have the same batch_size
     CHECK_EQ(inouts[0].dims_[0], inputs[1].dims_[0]);
     /// dim of output = dim of input * context_length
-    CHECK_EQ(inputs[1].dims_[1], inputs[0].dims_[1] * context_length_);
+    CHECK_EQ(inputs[1].dims_[1], inouts[0].dims_[1] * context_length_);
 
     typename SequenceT<Device>::type seq_vec(
         inputs[0].dims_[0], reinterpret_cast<int*>(inputs[0].getData()));