tdf#160176 svx: Reset help text when form control has none

In `FmFormPage::RequestHelp`, also call
`Help::ShowQuickHelp`/`Help::ShowBalloon` when
the help text is empty, as that is the way to
unset the help text/remove the tooltip again,
see `ImplShowHelpWindow` in `vcl/source/app/help.cxx`:

For the case of non-native tooltips (e.g. the
gen VCL plugin on Linux), the `bRemoveHelp = true`
code path is relevant.
For qt5/qt6/kf5/kf6 which use native tooltips,
the call to

pParent->ImplGetFrame()->ShowTooltip(rHelpText, rHelpArea)

further up sets the `QtFrame`'s `m_aTooltipText` member
to an empty string, which prevents showing the outdated
help text for the `QEvent::ToolTip` event in
`QtWidget::handleEvent`.

Change-Id: Iceb2424d9c72ae46333a718c677629122e517f11
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/166006
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

0 files changed, 0 insertions, 0 deletions