No need to check whether the pointer is NULL before deleting it nor to assign
NULL to it if it's going to be immediately reassigned on the next line.
Closes#11149.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61772 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775