cache playername on login

src/main/java/me/ryanhamshire/GriefPrevention/GriefPrevention.java

@@ -2966,6 +2966,7 @@ public class GriefPrevention extends JavaPlugin
     static void cacheUUIDNamePair(UUID playerID, String playerName)
     {
         //store the reverse mapping
+        playerNameCache.put(playerID, playerName);
         GriefPrevention.instance.playerNameToIDMap.put(playerName, playerID);
         GriefPrevention.instance.playerNameToIDMap.put(playerName.toLowerCase(), playerID);
     }