Fix `task_executor_initialize` in resource exhausted scenario. (#18609)

If we fail to create the event pool, this can leave the poller in an
uninitialized state and cleanup to report the failing status assumed it
was fully initialized in one place, causing an assert/abort.

Signed-off-by: Stella Laurenzo <stellaraccident@gmail.com>

runtime/src/iree/task/poller.c

diff --git a/runtime/src/iree/task/poller.c b/runtime/src/iree/task/poller.c
index 7fc9b47..e314379 100644
--- a/runtime/src/iree/task/poller.c
+++ b/runtime/src/iree/task/poller.c
@@ -130,8 +130,8 @@
 void iree_task_poller_deinitialize(iree_task_poller_t* poller) {
   IREE_TRACE_ZONE_BEGIN(z0);
 
-  // Must have called request_exit/await_exit.
-  IREE_ASSERT_TRUE(iree_task_poller_is_zombie(poller));
+  // Must have not been fully initialized or called request_exit/await_exit.
+  IREE_ASSERT_TRUE(!poller->thread || iree_task_poller_is_zombie(poller));
 
   iree_thread_release(poller->thread);
   poller->thread = NULL;