Don't throw errors when attempting to remove permission attachments

(bukkit will have already removed it).

EssentialsGroupManager/src/Changelog.txt

@@ -163,4 +163,5 @@ v 1.9:
 	- Prevent Null entries in group inheritance from throwing errors.
 v 2.0:
 	- Fix GM reporting of permission inheritance to retain the correct order. Lower inheritance groups can no longer negate a higher groups permissions.
-	- Fix an error I caused trying to modify an unmodifiable list when parsing '*' permissions.
+	- Fix an error I caused trying to modify an unmodifiable list when parsing '*' permissions.
+	- Don't throw errors when attempting to remove permission attachments (bukkit will have already removed it).

EssentialsGroupManager/src/org/anjocaido/groupmanager/permissions/BukkitPermissions.java

@@ -351,7 +351,14 @@ public class BukkitPermissions {
 	 */
 	private void removeAttachment(Player player) {
 		if (attachments.containsKey(player)) {
-			player.removeAttachment(attachments.get(player));
+			try {
+				player.removeAttachment(attachments.get(player));
+			} catch (IllegalArgumentException e) {
+				/*
+				 * Failed to remove attachment
+				 * This usually means Bukkit no longer know of it.
+				 */
+			}
 			attachments.remove(player);
 		}
 	}