cbsd up fails on base source selection if base not yet there #878

Describe the bug:

If base not avaliable locally - cbsd up fails with strange error, not allowing to select base source:

# cbsd up ver=13.8
invoking command:  /usr/bin/env cbsd_workdir=/jails jcreate jname=empty ... ver=13.8
no base dir in: /jails/basejail/base_amd64_amd64_13.8
Select base sources:
 0 .. CANCEL
 1 .. build
 1 .. extract
 1 .. pkg
 1 .. repo

select_getbase: no valid source
No base data on: /jails/basejail/base_amd64_amd64_13.8
# cbsd bases | fgrep 13.8
#

w/a - download base first with cbsd jcreate ver=<ver> than cbsd up will succeed

CBSD and Platform (OS version) (paste cbsd version && uname -msr output):

# cbsd version && uname -msr
15.0.5
FreeBSD 14.4-RELEASE-p6 amd64
#

Steps to reproduce?:

1. take any forlder with valid CBSDFile
2. select some FreeBSD verions that not yet in local bases
3. run cbsd up ver=<ver>

see

select_getbase: no valid source

instead of dialog about where from source base