Problem with onCommand from console sender

PHP:

package test3;
 
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.ChatColor;
import org.bukkit.Bukkit;
 
public class Test3 extends JavaPlugin {
   
    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args){
        Player t = Bukkit.getPlayer(args[0]);
            if (cmd.getName().equalsIgnoreCase("fly")){
                if (sender instanceof Player) {
                    Player p = (Player) sender;
                    if (args.length == 0){
                    if (!p.getAllowFlight()){
                        p.setAllowFlight(true);
                        p.sendMessage(ChatColor.GOLD + "Flight Enabled");
                    }else{
                        p.setAllowFlight(false);
                        p.sendMessage(ChatColor.GOLD + "Flight Enabled");
                    }
                    }else{
                        if (args.length == 1){
                            if (t.getAllowFlight()){
                                t.setAllowFlight(true);
                            }else{
                                t.setAllowFlight(false);
                            }
                    }
                    }
                }else{
                    sender.sendMessage("You must be a player");
                    return false;
                }
            }
            return true;
    }
}

The message you must be a player only works if the args == 1 isnt in the code. When I run the command with the args == 1 in, I get the error "unhandled exception executing command"

 

check your braces, you've got a mismatch somewhere

 

else {
sender.sendMessage("You must be a player!");
return true;
}

check if target is online!
if(t.isOnline() {

 

If the player isn't online, it's gonna cause errors I think.

Use if(t != null) instead.

 

simply use else { and send him a message when the target isn't online, then there wouldn't be any errors I think.
If yes - sorry I'm not perfect