tdf#91389 EDITING: Crash when deleting header

Replaced MyDlg(pParent).Execute by VclPtr equivalent

Change-Id: I7e03913665f770d694f53949e08425ba60adc6ad
Reviewed-on: https://gerrit.libreoffice.org/15908Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>

sw/source/uibase/wrtsh/wrtsh1.cxx

@@ -1771,12 +1771,13 @@ void SwWrtShell::ChangeHeaderOrFooter(
 
                 vcl::Window* pParent = &GetView().GetViewFrame()->GetWindow();
                 short nResult;
-                if (bHeader)
-                    nResult = DeleteHeaderDialog(pParent).Execute();
-                else
-                    nResult = DeleteFooterDialog(pParent).Execute();
-                bExecute = nResult == RET_YES;
+                if (bHeader) {
+                    nResult = ScopedVclPtrInstance<DeleteHeaderDialog>::Create(pParent)->Execute();
+                } else {
+                    nResult = ScopedVclPtrInstance<DeleteFooterDialog>::Create(pParent)->Execute();
+                }
 
+                bExecute = nResult == RET_YES;
                 StartAllAction();
             }
             if( bExecute )