tdf#93487 - protect GetFocus method call post dispose.

Change-Id: Id61e37e4e9ea62c3dba224e55ddfdc71fb0bfc8c
Reviewed-on: https://gerrit.libreoffice.org/19542Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Tested-by: Stephan Bergmann <sbergman@redhat.com>
(cherry picked from commit a3a61471)

svx/source/tbxctrls/tbcontrl.cxx

@@ -1638,7 +1638,8 @@ vcl::Window* SvxFrameWindow_Impl::GetPreferredKeyInputWindow()
 
 void SvxFrameWindow_Impl::GetFocus()
 {
-    aFrameSet->GrabFocus();
+    if (aFrameSet)
+        aFrameSet->GrabFocus();
 }
 
 void SvxFrameWindow_Impl::DataChanged( const DataChangedEvent& rDCEvt )