Crash when breaking random item box with no sidekick or stocks in Encore Mode

[MegAmi24]

Steps to reproduce:

1. Boot up game, start a new game in Encore Mode
2. When you get to GHZ, die as one of the characters, don't get any new stocks before or afterwards
3. Break a random item box

https://github.com/user-attachments/assets/913ff3c8-417e-4afc-836f-df4b3d5c61f9

[MegAmi24]

Looked in VS Debugger, there are two things causing this:

1. The game is supposed to play the swap fail sfx when there is no P2, but for some reason the check for it always returns false. My guess is there's an error in HUD_CharacterIndexFromID. https://github.com/RSDKModding/Sonic-Mania-Decompilation/blob/75b3784141d89668eaabce5173862993cecb8d53/SonicMania/Objects/Global/ItemBox.c#L591-L596

2. There's an infinite loop in the randomizing code, with the if ((1 << newPlayerIDs[p]) & globals->characterFlags) check always returning false and p never incrementing. This was also reported in #264. https://github.com/RSDKModding/Sonic-Mania-Decompilation/blob/75b3784141d89668eaabce5173862993cecb8d53/SonicMania/Objects/Global/ItemBox.c#L607-L614

[Mefiresu]

Fixed by https://github.com/RSDKModding/RSDKv5-Decompilation/commit/a80e2ba8600b210f79208bf5d3bd357627f5d63d

Explanation:

• To destroy an entity, the game usually calls ResetEntity with TYPE_BLANK as classID, which is DefaultObject.
• The engine takes the entity pointer, retrieves the size of the given classID (TYPE_BLANK here), and retrieves the entityClassSize for this classID. It then uses this size to run a memset(0) on the entity.
• The bug was triggered because DefaultObject was registered with a size of sizeof(ObjectDefaultObject) == 0x58, which is valid in pre-plus but was changed starting with Plus to account for the largest possible size for an entity sizeof(EntityBase) == 0x458.

In Encore mode, when you die, the game will swap your current character with the sidekick, and then reset the dead character's entity. The random item box tries to check for the characterID of the sidekick, but since it has been reset, we actually expect 0. The part of memory that was storing the characterID never got erased because of the smaller DefaultObject size, so it returned the old value, causing a softlock.