sw: fix warning C6011: Dereferencing NULL pointer 'rDoc.GetDocShell()'
E: /jenkins/workspace/lo_tb_master_win_analyze/sw/source/core/ole/ndole.cxx(775): error C2220: the following warning is treated as an error
E: \jenkins\workspace\lo_tb_master_win_analyze\sw\source\core\ole\ndole.cxx(759) : warning C6011: Dereferencing NULL pointer 'rDoc.GetDocShell()'. : Lines: 759, 736, 740, 741, e:\jenkins\workspace\lo_tb_master_win_analyze\include\comphelper\storagehelper.hxx:88, e:\jenkins\workspace\lo_tb_master_win_analyze\sw\source\core\ole\ndole.cxx:745, 748, 752, 751, 755, 758, 759
Change-Id: I94066734f6ac55eb9660682872685b8a7f80b8e8
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/205339
Tested-by: Jenkins
Reviewed-by: Xisco Fauli <xiscofauli@libreoffice.org>