Qt5 applications do not enable IBus when the applications are launched as the saved session

Qt5 applications do not enable IBus when the applications are saved in the session and launched automatically in the next login.

To reproduce:
1. Log into KDE plasma 5.
2. Configure ibus-daemon to run automatically when the user log into the session.
E.g. im-chooser is available in Fedora.
3. Confirm konsole works with QT_IM_MODULE=ibus.
4. Do not exit konsole but log out the session to save konsole in the session.
5. Log into the KDE again.

konsole runs automatically and ibus-daemon runs automatically but konsole does not enable ibus while QT_IM_MODULE=ibus is set correctly.