A recent security fix to ibus (CVE-2019-14822, #940267, DSA-4525-1)
exposed an interoperability bug between GLib's implementation of D-Bus
and the reference implementation libdbus (#941018). The practical
impact
is that Qt clients cannot use the updated ibus input method until GLib
is fixed.
This has been fixed in the upstream master and 2.62.x branches and
in unstable, and I've prepared backports for buster (this bug)
and stretch (I'll open a separate bug when I have a successful
build/autopkgtest/piuparts pipeline).