Created attachment 373765 [details]
A file with transaction descriptions in Cyrillic, can be used for repro steps.

Steps to reproduce if you have any Cyrillic keyboard layout installed
---------------------------------------------------------------------
1. Load the attached file.
2. Open 'Expenses' or 'Checking account'. There should be 30 entries, one for each letter of the Bulgarian alphabet.
3. Type (not paste) any Cyrillic letter in the description field of a new transaction, for example 'Г'.

Actual results
--------------
Autocomplete will fill in a suggestion ('Грозде'), put the cursor at the start of the entry, and select the entire entry.
If you now type another letter, say 'И', 'Грозде' will be replaced with 'Извара'.
If you continue typing letters matching the existing entries, autocomplete will just cycle through suggestions, preventing you from entering any text.

Expected results
----------------
After filling in a suggestion, autocomplete should put the cursor after the characters entered by the user and select only the characters after the cursor.
Continuing the example, if you type 'И' as a second letter, the description field should read 'ГИ'.

Note
----
I tried several other non-ASCII characters and also managed to trigger the issue so if you don't have a Cyrillic layout, you may be able to reproduce the issue with any other non-ASCII entries.

(This is different from issue 796734 where the autocompleted characters are not selected at all.)