update the code check for the detetion_map_op, test=develop

paddle/fluid/operators/detection_map_op.cc

@@ -68,12 +68,12 @@ class DetectionMAPOp : public framework::OperatorWithKernel {
           ctx->HasInput("TruePos"),
           platform::errors::InvalidArgument(
               "Input(TruePos) of DetectionMAPOp should not be null when "
-              "Input(TruePos) is not null."));
+              "Input(PosCount) is not null."));
       PADDLE_ENFORCE(
           ctx->HasInput("FalsePos"),
           platform::errors::InvalidArgument(
               "Input(FalsePos) of DetectionMAPOp should not be null when "
-              "Input(FalsePos) is not null."));
+              "Input(PosCount) is not null."));
     }
 
     ctx->SetOutputDim("MAP", framework::make_ddim({1}));