Fix NPE in PermissionsHandler#getGroups(OfflinePlayer)

[phinner]

Information

NPEs will occur if PermissionsHandler.handler#getGroups(OfflinePlayer) returns null.
Which is the case if PermissionsHandler.handler is SuperpermsHandler for example.
This results in console spam which is quite unpleasant :(.

Example:

[15:03:48] [Craft Scheduler Thread - 10 - Essentials/WARN]: [Essentials] Plugin Essentials v2.22.0-dev+53-9ad754b generated an exception while executing task 53
java.lang.NullPointerException: Cannot invoke "java.util.Collection.toArray()" because "c" is null
	at java.base/java.util.ArrayList.addAll(ArrayList.java:752) ~[?:?]
	at EssentialsX-2.22.0-dev+53-9ad754b.jar/com.earth2me.essentials.perm.PermissionsHandler.getGroups(PermissionsHandler.java:61) ~[EssentialsX-2.22.0-dev+53-9ad754b.jar:?]
	at EssentialsXDiscordLink-2.21.2.jar/net.essentialsx.discordlink.rolesync.RoleSyncManager.sync(RoleSyncManager.java:63) ~[EssentialsXDiscordLink-2.21.2.jar:?]
	at EssentialsXDiscordLink-2.21.2.jar/net.essentialsx.discordlink.rolesync.RoleSyncManager.lambda$new$0(RoleSyncManager.java:46) ~[EssentialsXDiscordLink-2.21.2.jar:?]
	at org.bukkit.craftbukkit.scheduler.CraftTask.run(CraftTask.java:78) ~[purpur-1.21.10.jar:1.21.10-2531-b7b7ba2]
	at org.bukkit.craftbukkit.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:57) ~[purpur-1.21.10.jar:1.21.10-2531-b7b7ba2]
	at com.destroystokyo.paper.ServerSchedulerReportingWrapper.run(ServerSchedulerReportingWrapper.java:22) ~[purpur-1.21.10.jar:?]
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[?:?]
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[?:?]
	at java.base/java.lang.Thread.run(Thread.java:1583) ~[?:?]

Details

Proposed fix:

The straighforward solution is to simply add a null check like the other methods of PermissionsHandler.

I also thought about copying and adapting the method body of PermissionsHandler#getGroups() such as

List<String> groups = handler.getGroups(base);
if (groups == null || groups.isEmpty()) {
  groups = Collections.singletonList(defaultGroup);
}

But that would change the behavior of PermissionsHandler#getGroups(OfflinePlayer) by no longer returning the default group as the first group, so I did not.

Environments tested:

OS: Linux (docker)

Java version: 21

• Most recent Paper version (1.XX.Y, git-Paper-BUILD)
• CraftBukkit/Spigot/Paper 1.12.2
• CraftBukkit 1.8.8
• Purpur 1.21.10-2531-HEAD@b7b7ba2 (Implementing API version 1.21.10-R0.1-SNAPSHOT)

Demonstration:

N/A, the log spam just stops.