Fix call of ippiConvert.

modules/core/src/convert.cpp

@@ -1083,20 +1083,26 @@ dtype* dst, size_t dstep, Size size, double* scale) \
 #define DEF_CVT_FUNC_F(suffix, stype, dtype, ippFavor) \
 static void cvt##suffix( const stype* src, size_t sstep, const uchar*, size_t, \
                          dtype* dst, size_t dstep, Size size, double*) \
+{ \
+    if (src && sstep && dst && dstep && size.width && size.height)\
     {\
         if (ippiConvert_##ippFavor(src, (int)sstep, dst, (int)dstep, ippiSize(size.width, size.height)) >= 0) \
             return; \
         setIppErrorStatus(); \
+    }\
     cvt_(src, sstep, dst, dstep, size); \
 }
 
 #define DEF_CVT_FUNC_F2(suffix, stype, dtype, ippFavor) \
 static void cvt##suffix( const stype* src, size_t sstep, const uchar*, size_t, \
                          dtype* dst, size_t dstep, Size size, double*) \
+{ \
+    if (src && sstep && dst && dstep && size.width && size.height)\
     {\
         if (ippiConvert_##ippFavor(src, (int)sstep, dst, (int)dstep, ippiSize(size.width, size.height), ippRndFinancial, 0) >= 0) \
             return; \
         setIppErrorStatus(); \
+    }\
     cvt_(src, sstep, dst, dstep, size); \
 }
 #else