Avoid some warnings during compilation

[remkos]

Description of proposed changes

This just avoids some warnings during compilation (at least under MacOS).
There is no change in functionality.

Reminders

• Make sure that your code follows our style. Use the other functions/files as a basis.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Describe changes to function behavior and arguments in a comment below the function declaration.
• If adding new functionality, add a detailed description to the documentation and/or an example.

[joa-quim]

I Have a bunch of new warning with VS that I must shut up too.