Shell : Drive popup menu can't be opened if a drive properties page is opened

reactos-bootcd-0.4.15-dev-6000-g8b948ff-x86-gcc-lin-dbg

Related to CORE-4217

• Open "My Computer"
• Open C: Drive properties
• Right click on D:
• nothing happens
• Log shows : "err:(dll/win32/shell32/CDefView.cpp:1589) HACK: Aborting context menu in nested call!" introduced by learn_more in https://github.com/reactos/reactos/commit/544b7344982bdd6a1e1180e1a9964744ff0653b0 
• expected result : popup menu is displayed
• changing directory to C: then coming back to My Computer re-enable popup menu

0.4.15-dev-5126-g3bb451b
0.4.15-dev-5127-g544b734
Guilty commit is 544b734 / https://github.com/reactos/reactos/commit/544b7344982bdd6a1e1180e1a9964744ff0653b0 by learn_more