This disable will be done, in a better way, by the call to
BrowseBox::MouseButtonDown below, *after* the destination of the mouse
click has grabbed the focus, by a call to DeactivateCell().

If this is done here, while the "source" controller still has the
focus, then the window's Disable() method will try to pass the focus
the the "next control". However, the "next" control may belong to
another form, and this will do a (premature!) save to the database of
the modifications. This may lead to a database error, when the data is
not in a shape to be written to the database, e.g. when on an
insertion row and not all mandatory fields have been filled in.
This then pops up an error message to the user.

Change-Id: I38b1850319691b34232e51f131f8d099dc4a9114
Reviewed-on: https://gerrit.libreoffice.org/17270Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>