bus: do not print (null) if the message has unknown type
(cherry picked from commit e8fd7e4b5b5269377efc641a7da43850822c1250)
Resolves: #1696224
patch_name: 0166-bus-do-not-print-null-if-the-message-has-unknown-typ.patch
present_in_specfile: true
location_in_specfile: 166
squash_commits: true