core: fix gcc7 warning about empty VA_ARGS in Assert macro

modules/core/include/opencv2/core/base.hpp

@@ -426,7 +426,7 @@ configurations while CV_DbgAssert is only retained in the Debug configuration.
 */
 
 #define CV_VA_NUM_ARGS_HELPER(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, N, ...)    N
-#define CV_VA_NUM_ARGS(...)      CV_VA_NUM_ARGS_HELPER(__VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1)
+#define CV_VA_NUM_ARGS(...)      CV_VA_NUM_ARGS_HELPER(__VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
 
 #define CV_Assert_1( expr ) if(!!(expr)) ; else cv::error( cv::Error::StsAssert, #expr, CV_Func, __FILE__, __LINE__ )
 #define CV_Assert_2( expr1, expr2 ) CV_Assert_1(expr1); CV_Assert_1(expr2)