refactor(zc): only check already loaded saves for 4th qst red easter egg

Otherwise, it takes noticeable time to load every save file when the
file select screen loads.

Author: connorjclark

src/zc/saves.cpp

@@ -2153,6 +2153,15 @@ int32_t saves_current_selection()
 	return currgame;
 }
 
+bool saves_is_slot_loaded(int32_t index, bool full_data)
+{
+	if (saves.size() <= index)
+		return false;
+	if (full_data && saves[index].game == nullptr)
+		return false;
+	return saves[index].header != nullptr;
+}
+
 const save_t* saves_get_slot(int32_t index, bool full_data)
 {
 	save_t* save;

src/zc/saves.h

@@ -45,6 +45,7 @@ int32_t saves_count();
 int32_t saves_current_selection();
 bool saves_create_slot(gamedata* game, bool save_to_disk = true);
 bool saves_create_slot(fs::path path);
+bool saves_is_slot_loaded(int32_t index, bool full_data = false);
 const save_t* saves_get_slot(int32_t index, bool full_data = false);
 const save_t* saves_get_current_slot();
 void saves_delete(int32_t index);

src/zc/title.cpp

@@ -283,11 +283,25 @@ static void list_saves()
 {
 	// Fourth Quest turns the menu red.
 	bool red = false;
-	
+
+	// First, make sure the presently listed quests are loaded.
 	int savecnt = saves_count();
+	for(int32_t i=0; i<3; i++)
+	{
+		int j = listpos+i;
+		if (j < savecnt)
+			saves_get_slot(j);
+	}
+
+	// Check if any loaded quests is the 4th quest.
 	for(int32_t i=0; i<savecnt; i++)
-		if (saves_get_slot(i)->header && saves_get_slot(i)->header->quest == 4)
+	{
+		if (saves_is_slot_loaded(i) && saves_get_slot(i)->header->quest == 4)
+		{
 			red = true;
+			break;
+		}
+	}
 
 	loadpalset(0,red ? pSprite(spPILE) : 0);