Addressing compiler warning: comparing a pointer to a null character constant

[jonasbn]

I fell over a warning and GH copilot came up with a suggestion for fix.

This PR addresses the compiler warning:

• comparing a pointer to a null character constant; did you mean to compare to NULL? [-Wpointer-compare]

I have submitted this as a separate PR, since it did not belong in the other PR I sent you today.

Please review and see if it makes sense. My tests demonstrate that the code still works are expected with the suggested implementation.