core: fix display bugs with non-printable chars like tabs (part of messages not displayed) (bug #38076)

This bug was introduced by commit 70ce7fe3b6caa6128cb6e8bfb0eaaf39f1ebe4ce.
core: fix click in item "buffer_nicklist" when nicklist is a root bar (bug #38080)

Argument "*" is now silently ignored in command /window.

When item "buffer_nicklist" is in a root bar, we use current window/buffer to
find which nick has been clicked (same behaviour as callback used to display bar
item "buffer_nicklist").
Version 0.4.0-rc3