Fix: potential bucket corruption in timer reset_buckets (#17231)

Co-authored-by: Simon Ogorodnik <simon.ogorodnik@gmail.com>

code/controllers/subsystem/timer.dm

@@ -265,6 +265,12 @@ SUBSYSTEM_DEF(timer)
 	// Add all timed events from the secondary queue as well
 	alltimers += second_queue
 
+	for (var/datum/timedevent/t in alltimers)
+		t.bucket_joined = FALSE
+		t.bucket_pos = -1
+		t.prev = null
+		t.next = null
+
 	// If there are no timers being tracked by the subsystem,
 	// there is no need to do any further rebuilding
 	if (!length(alltimers))
@@ -308,6 +314,7 @@ SUBSYSTEM_DEF(timer)
 		new_bucket_count++
 		var/bucket_pos = BUCKET_POS(timer)
 		timer.bucket_pos = bucket_pos
+		timer.bucket_joined = TRUE
 
 		var/datum/timedevent/bucket_head = bucket_list[bucket_pos]
 		if (!bucket_head)