v7.1.4-rc.3: nil check for block (#16825)

What type of PR is this? Bug fix What does this PR do? Why is it needed? fetchOriginSidecars : Check if block is nil . Which issues(s) does this PR fix? (Partially) fixes: #16824 I don't know why the block was not found is the DB. But at least now in such a case it won't panic. Acknowledgements I have read CONTRIBUTING.md . I have included a uniquely named changelog fragment file . I have added a…