Change implicit conversion to explicit conversion to remove warning

[masnm]

I was using raylib in one of my project which i was compiling with clang and clang showed an warning about the implicit conversion. So making a PR to get rid of the warning and to help the project in a negligible way.

[raysan5]

@masnm Thanks for the review but note this change could be overwritten on par_shapes update, this change should be sent to the library main repo.