Allow offline players for chat events.

This fixes issues with plugins or applications that rely on JSONAPI to
chat. Fixes #1578

src/main/java/com/gmail/nossr50/listeners/PlayerListener.java

@@ -618,7 +618,7 @@ public class PlayerListener implements Listener {
             return;
         }
 
-        McMMOPlayer mcMMOPlayer = UserManager.getPlayer(player);
+        McMMOPlayer mcMMOPlayer = UserManager.getPlayer(player, true);
         ChatManager chatManager = null;
 
         if (mcMMOPlayer.getPartyChatMode()) {

src/main/java/com/gmail/nossr50/util/player/UserManager.java

@@ -90,6 +90,10 @@ public final class UserManager {
         return retrieveMcMMOPlayer(player.getName(), false);
     }
 
+    public static McMMOPlayer getPlayer(OfflinePlayer player, boolean offlineValid) {
+        return retrieveMcMMOPlayer(player.getName(), offlineValid);
+    }
+
     public static McMMOPlayer getPlayer(String playerName, boolean offlineValid) {
         return retrieveMcMMOPlayer(playerName, offlineValid);
     }