Bug 427853

SUMMARY
Typing a special character in the recipients text field saturates the system.

STEPS TO REPRODUCE
1. Launch KMail
2. Create a new mail
3. In the text field nex to "to/cc/cci" (recipients), enter a special character (i.e ç or â)

OBSERVED RESULT
4a. Press Enter
5a.
KMail adds all my addresses (which are in the KAddressBook) to the recipients list indefinitely.
Then, once the maximum amount of recipients is reached (200), the message box (which says that) continues to show up billions of times and saturates the system (Clicking on "OK" does nothing, as I can't click faster than the system).

4b. Remove the "focus" from the "new message" KMail window (click on the application launcher, open a Konsole, or click on a already opened window like the main KMail [where the inbox is])
5b. Kmail adds, ONLY ONCE, all my addresses (which are in the KAddressBook) to the recipients list.

EXPECTED RESULT
Nothing, the special character stays in the text field, same as if we had a typed a normal ASCII-compatible character.

SOFTWARE/OS VERSIONS
Linux: Arch Linux 5.4.71.1-lts x86_64
KDE Plasma Version: 5.20.0
KDE Frameworks Version: 5.75.0
Qt Version: 5.15.1

ADDITIONAL INFORMATION
Laptop model: HP ProBook 450 G4
CPU: i5-7200U
RAM: 8GB
GPU: Mesa Intel HD graphics

Everything in KMail is set to UTF-8;
Configuration->Configure KMail->Editor->Encodings:
- utf8 (locale)
- utf8

locale:
everything (LANG, LC_xxx) is set to "fr_CH.UTF-8" but LC_ALL.

Be aware that some terms may not be exactly the same, because I translated them from french to english.