[SHELL32] -CMenuToolbarBase: Remove all buttons on destruction. CORE-13194

It seems that TBN_DELETINGBUTTON isn't called when the toolbar gets destroyed so the only way to avoid leaking the data is emptying it ourselves.

dll/win32/shell32/shellmenu/CMenuToolbars.cpp

@@ -287,6 +287,8 @@ CMenuToolbarBase::CMenuToolbarBase(CMenuBand *menuBand, BOOL usePager) :
 
 CMenuToolbarBase::~CMenuToolbarBase()
 {
+    ClearToolbar();
+
     if (m_hWnd)
         DestroyWindow();