journal-gateway: use localStorage["cursor"] only when it has valid value
Discovered by LGTM.
(cherry picked from commit 944072feddb73333023d0a98bf87fd2a17f894d3)
Resolves: #1705971
patch_name: 0200-journal-gateway-use-localStorage-cursor-only-when-it.patch
present_in_specfile: true
location_in_specfile: 200
squash_commits: true