gui: _chat_word in hook_focus callback hashtable offset when prefix_align is none

[sim642]

In the process of putting together a trigger for opening URLs from cursor mode I noticed behavior where ${_chat_word} in the hook_focus callback hashtable contains data which wasn't exactly under the cursor, but offset a bit. This only seems to be wrong when prefix_align option is set to none.

Same problem affects ${_chat_bol} and ${_chat_eol}.

It is possible to see this being wrong with /debug cursor.