How to reproduce:
Either on the command line, or in any other text entry field (e.g. copy
file to) enter a string where the last word consists of one single
letter only. E.g. "abc de f".
Press Alt+Backspace.
Expected behavior: Remove the last word, that is, the letter "f" only,
leaving "abc de ".
Actual behavior: Yet another word is removed, leaving "abc ".
Signed-off-by: Andrew Borodin <aborodin@vmail.ru>