Add initial value for shell variable

[luca-vercelli]

Condition

if [ $disable_precise_later == true ]; 

gives a syntax error if variable is not initialized

Contributor license agreement signed?

Yes

[forslund]

This definitely seems like the correct thing to do.

I think #3060 fixes the same issue (in a different way) should both of these fixes be merged...both initializing the value and using double brackets?

Edit: Shellcheck is ok with either solution so no need to change anything

[krisgesling]

Thanks Luca!

I'm just retriggering fresh builds - I think we're all clear at the moment so should be able to merge this shortly.

[devops-mycroft]

Voight Kampff Integration Test Succeeded (Results)