Handle non-initialized pImplSVData in InitAppFontData

If pSVData->maWinData.mpFirstFrame is null in
Application::InitAppFontData() then we need to create a new WorkWindow.

Change-Id: I6665ff6525321554c8fd4943ec623978ce35f168
Reviewed-on: https://gerrit.libreoffice.org/9272
Reviewed-by: Tor Lillqvist <tml@collabora.com>
Tested-by: Tor Lillqvist <tml@collabora.com>