What version of unit.c are you referring to? Looks like this issue has been fixed by Jan Engelhard in 2017, see this commit: https://sourceforge.net/p/libdbi-drivers/libdbi-drivers/ci/470b58e15dc6f406899b1695aec7fc98986b8f14/
updated for release 1.0.3
updated PHP interface setup
initialize ELVALUE to silence a boatload of overzealous warnings; minor code cleanup
fixed old http:// URLs
oops - XIncludes must not use https
updated documentation for 1.0.3
removed debug printf() call