BUG/MINOR: acme: null pointer dereference upon allocation failure

BUG/MINOR: acme: null pointer dereference upon allocation failure

Reported in issue #3115:

     	11. var_compare_op: Comparing task to null implies that task might be null.
681                if (!task) {
682                        ret++;
683                        ha_alert("acme: couldn't start the scheduler!\n");
684                }
CID 1609721: (#1 of 1): Dereference after null check (FORWARD_NULL)
12. var_deref_op: Dereferencing null pointer task.
685                task->nice = 0;
686                task->process = acme_scheduler;
687
688                task_wakeup(task, TASK_WOKEN_INIT);
689        }
690

Task would be dereferenced upon allocation failure instead of falling
back to the end of the function after the error.

Should be backported in 3.2.