Correct the bug found for the installation of ScriptRepository

Ubuntu used to define non initialized bool attribute as false, but, windows
does seems to initialize them as true. So, the error presented by the test:

{{{
ScriptRepository: Corrupted database : .repository.json
}}}

was not seem at my development environment (ubuntu). This commit does
initialize the valid attribute to fix this issue.

re #6923
Merge branch 'bugfix/6923_auto_update' into develop