Since d8bddb9 some SAPI would only
setup/reset callbacks to libxml once, instead of for each request
processed. However, this also included a callback for structured
errors, which should remain per request (as it can be defined through
As a result, after the internal handler was set in a request,
processing another request would result in the handler being triggered
while the memory associated with it (LIBXML(error_list)) had been
free-d/reset, leading to the process segfaulting.
This reset the handler for structured errors after each request.
(Bug #61325 might possibly also be the same bug)