Fixes compilation errors when BUILD_CUDA_STUBS is ON

modules/cudaoptflow/src/tvl1flow.cpp

@@ -42,15 +42,15 @@
 
 #include "precomp.hpp"
 
+using namespace cv;
+using namespace cv::cuda;
+
 #if !defined HAVE_CUDA || defined(CUDA_DISABLER)
 
 Ptr<OpticalFlowDual_TVL1> cv::cuda::OpticalFlowDual_TVL1::create(double, double, double, int, int, double, int, double, double, bool) { throw_no_cuda(); return Ptr<OpticalFlowDual_TVL1>(); }
 
 #else
 
-using namespace cv;
-using namespace cv::cuda;
-
 namespace tvl1flow
 {
     void centeredGradient(PtrStepSzf src, PtrStepSzf dx, PtrStepSzf dy, cudaStream_t stream);