chore: static_cast to fix sign conversion warning

[evan-goode]

Without this patch, the i686 build fails due to -Werror and a sign conversion warning, introduced in #1703.

I only noticed the error after making an upstream release and trying to build DNF 5.2.6.1 in Koji. It might be good to have builds for non-x86_64 architectures tested in our upstream CI so we can catch these issues sooner.

[jrohel]

Without this patch, the i686 build fails due to -Werror and a sign conversion warning

On x86_64, std::vector<some_type>::difference_type is a 64 bit signed type. Thus it can hold a larger number than unsigned int, a 32 bit unsigned type.
But, on i686, std::vector<some_type>::difference_type is a 32 bit signed type. So the compiler correctly warned when adding unsigned int - a 32 bit unsigned type.

It might be good to have builds for non-x86_64 architectures tested in our upstream CI.

Yes, good idea. Especially testing a 32 bit build.

We could also test builds for big-endian architecture. To catch endian related bugs. Fedora supports s390x - big-endian architecture.

[jrohel]

Thanks for the fix.