Fix failing --no-check-version cli option

Currently, if the --no-check-version option is used,
the scan fails because an unbound variable is passed to
the run_scan function.
Fix this by assigning None in that case. Add a test that
passes with this change and fails without it.

Signed-off-by: alexzurbonsen <alexander.zur.bonsen@tngtech.com>

Author: alexzurbonsen