Merge branch 'fixmail' into unstable
# Conflicts:
# src/main/java/emu/grasscutter/game/mail/Mail.java
# src/main/java/emu/grasscutter/net/packet/PacketOpcodes.java
# src/main/java/emu/grasscutter/server/packet/recv/HandlerGetAllMailReq.java
# src/main/java/emu/grasscutter/server/packet/send/PacketGetAllMailRsp.java
# src/main/java/emu/grasscutter/utils/Utils.java