Fix buried larva spawn grace period at start of round (#4988)

# About the pull request

Looking at the code again, #4502 is unintentionally eliminating the
buried larva grace period when there is no core. The first 30 minutes
should have a core be optional (because the hive is still being
established), but the queue requires a core (or nested bodies) to
dequeue players from the queue. So as soon as there is one player in
queue, buried spawns during the no-core grace period would be stopped.

This PR makes it so the queue will only prevent manual buried spawns
when there is a core.

# Explain why it's good for the game

Fixes a situation that needlessly hinders xeno start if the hive puts
off creating a core.

Also the logic was getting fairly complex here so the early returns
should make it more manageable.

# Testing Photographs and Procedure
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<summary>Screenshots & Videos</summary>

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screenshots and the `<details>` tags.

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# Changelog
:cl: Drathek
fix: Fixed buried larva spawn grace period at start of round if there is
a queue: Now join as xeno when there's a queue will only prevent buried
larva spawns if there is no core.
/:cl:

code/game/gamemodes/cm_initialize.dm

@@ -356,21 +356,27 @@ Additional game mode variables.
 		else
 			available_xenos_non_ssd += cur_xeno
 
-	// Only offer buried larva if there is no queue:
-	// This basically means this block of code will almost never execute, because we are instead relying on the hive cores/larva pops to handle their larva
-	// Technically this should be after a get_alien_candidates() call to be accurate, but we are intentionally trying to not call that proc as much as possible
-	if(GLOB.xeno_queue_candidate_count < 1)
-		var/datum/hive_status/hive
-		for(var/hivenumber in GLOB.hive_datum)
-			hive = GLOB.hive_datum[hivenumber]
-			if(!hive.hardcore && hive.stored_larva && (hive.hive_location || (world.time < XENO_BURIED_LARVA_TIME_LIMIT + SSticker.round_start_time)))
-				if(SSticker.mode && (SSticker.mode.flags_round_type & MODE_RANDOM_HIVE))
-					available_xenos |= "any buried larva"
-					LAZYADD(available_xenos["any buried larva"], hive)
-				else
-					var/larva_option = "buried larva ([hive])"
-					available_xenos += larva_option
-					available_xenos[larva_option] = list(hive)
+	var/datum/hive_status/hive
+	for(var/hivenumber in GLOB.hive_datum)
+		hive = GLOB.hive_datum[hivenumber]
+		if(hive.hardcore)
+			continue
+		if(!hive.stored_larva)
+			continue
+		// Only offer buried larva if there is no queue because we are instead relying on the hive cores/larva pops to handle their larva:
+		// Technically this should be after a get_alien_candidates() call to be accurate, but we are intentionally trying to not call that proc as much as possible
+		if(hive.hive_location && GLOB.xeno_queue_candidate_count > 0)
+			continue
+		if(!hive.hive_location && (world.time > XENO_BURIED_LARVA_TIME_LIMIT + SSticker.round_start_time))
+			continue
+
+		if(SSticker.mode && (SSticker.mode.flags_round_type & MODE_RANDOM_HIVE))
+			available_xenos |= "any buried larva"
+			LAZYADD(available_xenos["any buried larva"], hive)
+		else
+			var/larva_option = "buried larva ([hive])"
+			available_xenos += larva_option
+			available_xenos[larva_option] = list(hive)
 
 	if(!available_xenos.len || (instant_join && !available_xenos_non_ssd.len))
 		if(!xeno_candidate.client || !xeno_candidate.client.prefs || !(xeno_candidate.client.prefs.be_special & BE_ALIEN_AFTER_DEATH))