Fixed utimes segfault when given nullptr
Sqlite does a utimes(..., NULL)
when running in unix-dotfile
vfs. https://github.com/sqlite/sqlite/blob/48cca2422eaff80968966c29705222be8b061d72/src/os_unix.c#L2342
This is allowed and means "use current time" https://linux.die.net/man/2/utimes
Currently it incorrectly fails with a segfault.
Edited by Martin Welgemoed