ZERO WIDTH NON-JOINER and some other (space) characters cannot be entered in kate and other Qt5 apps

The ZERO WIDTH NON-JOINER character (U+200C) is very useful in arabic-like languages. However, if you assign a key to it and type it in a Qt5-base app eg KDE kate, nothing will be entered. However there is not such problem with gedit and other non-qt apps.

Reproducible: Always

Steps to Reproduce:
1. Switch to Arabic keyboard layout in Kububtu 16.04
2. Press shift+space between any Arabic word in `kate`.
3. Press shift+space between any Arabic word in `gedit`.
4. Compare the results.
5. Copy what you type in gedit and paste it in `kate`. There is no problem when pasting. Just typing ZERO WIDTH NON-JOINER and similar characters is prohibited in `kate`.

Actual Results:
Nothing is typed when you press a key assigned for typing ZERO WIDTH NON-JOINER in kate and other Qt5-based apps. There is no such problem in `gedit` and other gnome apps.

There was not such problem in KDE4 in Ubuntu 14.04. This issue is so important that one need to find qt4 compilation version instead of the normal version. In effect, many writing and typing qt5-based apps become unusable for some languages.