Fixed some issues found by static analysis

modules/core/src/rand.cpp

@@ -675,7 +675,7 @@ void RNG::fill( InputOutputArray _mat, int disttype,
 
     const Mat* arrays[] = {&mat, 0};
     uchar* ptr;
-    NAryMatIterator it(arrays, &ptr);
+    NAryMatIterator it(arrays, &ptr, 1);
     int total = (int)it.size, blockSize = std::min((BLOCK_SIZE + cn - 1)/cn, total);
     size_t esz = mat.elemSize();
     AutoBuffer<double> buf;