BUG/MINOR: acme: warning ‘ctx’ may be used uninitialized

BUG/MINOR: acme: warning ‘ctx’ may be used uninitialized

Please compiler with maybe-uninitialized warning

src/acme.c: In function ‘cli_acme_chall_ready_parse’:
include/haproxy/task.h:215:9: error: ‘ctx’ may be used uninitialized [-Werror=maybe-uninitialized]
  215 |         _task_wakeup(t, f, MK_CALLER(WAKEUP_TYPE_TASK_WAKEUP, 0, 0))
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/acme.c:2903:17: note: in expansion of macro ‘task_wakeup’
 2903 |                 task_wakeup(ctx->task, TASK_WOKEN_MSG);
      |                 ^~~~~~~~~~~
src/acme.c:2862:26: note: ‘ctx’ was declared here
 2862 |         struct acme_ctx *ctx;
      |                          ^~~

Backport to 3.2.