Incorrect behavior of itertools::product for empty range argument

### Description

When one of the ranges passed to `itertools::product` is an empty range, the resulting product range should be empty.
Currently this is not the case.

### Steps to Reproduce

This test currently fails
```c++
long count = 0;
for (auto [l, m] : product_range(0, 5)) ++count;
EXPECT_EQ(count, 0);
```

### Versions

d10e86d
