Server erroneously accepts actions from dead players

Even when a player is dead, the server will accept and process packets from them if they are sent (for example by using a modified client). This can lead to unexpected or malicious behavior in some circumstances. The best approach is to not handle such packets if the player is dead (for example: https://hub.spigotmc.org/stash/projects/SPIGOT/repos/craftbukkit/browse/nms-patches/PlayerConnection.patch#620 https://hub.spigotmc.org/stash/projects/SPIGOT/repos/craftbukkit/browse/nms-patches/PlayerConnection.patch#648 https://hub.spigotmc.org/stash/projects/SPIGOT/repos/craftbukkit/browse/nms-patches/PlayerConnection.patch#923 inter alia)

EDIT: inter alia: https://bugs.mojang.com/browse/MC-101272