After preloading has executed, the executor globals for class_table and
function_table are still referring to the values during preloading.
If no request happens after that then these values will remain dangling
pointers. If then the -v option on CLI or -h option (and possibly
others) on CGI is provided, there is a double free.
Fix it by nulling the pointers explicitly after preloading has finished
to fix it for all SAPIs.
Closes GH-12311.
