Related tdf#92322: fix crash with doCursor

0  0x00002aaaafaf3b0c in BrowseBox::DoShowCursor(char const*) (this=0x2f424e0) at /home/julien/compile-libreoffice/libreoffice/svtools/source/brwbox/brwbox1.cxx:182
1  0x00002aaaafafe392 in BrowseBox::GetFocus() (this=0x2f424e0) at /home/julien/compile-libreoffice/libreoffice/svtools/source/brwbox/brwbox1.cxx:2489
2  0x00002aaaafb27966 in svt::EditBrowseBox::GetFocus() (this=0x2f424e0) at /home/julien/compile-libreoffice/libreoffice/svtools/source/brwbox/editbrowsebox.cxx:237
3  0x00002aaab1b5706a in vcl::Window::CompatGetFocus() (this=0x2f424e0) at /home/julien/compile-libreoffice/libreoffice/vcl/source/window/window.cxx:3948
See https://bugs.documentfoundation.org/attachment.cgi?id=116859

Change-Id: I664884ee9333055707aecd7ad309c1a97596b71b
Reviewed-on: https://gerrit.libreoffice.org/16583Reviewed-by: Philippe Jung <phil.jung@free.fr>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

svtools/source/brwbox/brwbox1.cxx

@@ -179,6 +179,8 @@ short BrowseBox::GetCursorHideCount() const
 
 void BrowseBox::DoShowCursor( const char * )
 {
+    if (!getDataWindow())
+        return;
     short nHiddenCount = --getDataWindow()->nCursorHidden;
     if (PaintCursorIfHiddenOnce())
     {