Bukkit

What steps will reproduce the problem?
1. Install plugin
2. Use

What is the expected output? What do you see instead?
Without errors :)

What version of the product are you using?
Bukkit-1.4.6-R0.3
name: ShopAds2 version: 0.84

Do you have an error log of what happened?
2013-01-27 10:06:38 [SEVERE] Exception in thread "pool-1-thread-3030"
2013-01-27 10:06:38 [SEVERE] org.apache.commons.lang.UnhandledException: Plugin ShopAds2 v0.84 generated an exception while executing t
ask 5171
        at org.bukkit.craftbukkit.v1_4_6.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
        at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.NullPointerException
        at org.bukkit.plugin.PluginBase.getName(PluginBase.java:29)
        at org.bukkit.plugin.PluginBase.equals(PluginBase.java:25)
        at java.util.ArrayList.remove(ArrayList.java:481)
        at org.hpiz.ShopAds2.Shop.ShopHandler.removeShop(ShopHandler.java:121)
        at org.hpiz.ShopAds2.Util.Messaging.AdvertisementMessage.advertise(AdvertisementMessage.java:19)
        at org.hpiz.ShopAds2.Threads.AnnounceThread.run(AnnounceThread.java:80)
        at org.bukkit.craftbukkit.v1_4_6.scheduler.CraftTask.run(CraftTask.java:53)
        at org.bukkit.craftbukkit.v1_4_6.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53)
        ... 3 more

2013-01-27 10:06:59 [INFO] Donde...? issued server command: /back

Please provide any additional information below.
Probably because offline players have lots of f... strange nicknames