browser: Clear history owners _before_ opening urls.
browser: Clear history owners _before_ opening urls.

Before this fix, with restore-session-on-startup-p set to nil, all the owners
were after open-urls, thus deleting all the buffers, including new ones, from
history.

Adding to that, dummy buffer created on startup is an input-buffer, so we cannot
get its history-file and need to resort to history-file of *browser*.

jmercouris/NeXT,jmercouris/NeXT