unhaled exception on command type:-

[nasiridrishi]

git version :- 1b484c4
pmmp commit used (git):- f0b4a33 (latest release)
console error:-

2017-08-01 [13:20:08] [Server thread/INFO]: An unknown error occurred while attempting to 
           perform this command
          2017-08-01 [13:20:08] [Server thread/CRITICAL]: Unhandled exception executing command 'f' in 
         f: 
         Return value of FactionsPro\FactionMain::onCommand() must be of the type boolean, none 
         returned
         2017-08-01 [13:20:08] [Server thread/CRITICAL]: TypeError: "Return value of 
         FactionsPro\FactionMain::onCommand() must be of the type boolean, none returned" 
      (EXCEPTION) 
        in "FactionsPro.phar/src/FactionsPr```
Debug report:-

```20:08] [Server thread/DEBUG]: #0 src/pocketmine/command/PluginCommand(58): FactionsPro\FactionMain->onCommand(pocketmine\command\ConsoleCommandSender object, pocketmine\command\PluginCommand object, string f, array Array())
2017-08-01 [13:20:08] [Server thread/DEBUG]: #1 src/pocketmine/command/SimpleCommandMap(237): pocketmine\command\PluginCommand->execute(pocketmine\command\ConsoleCommandSender object, string f, array Array())
2017-08-01 [13:20:08] [Server thread/DEBUG]: #2 src/pocketmine/Server(1935): pocketmine\command\SimpleCommandMap->dispatch(pocketmine\command\ConsoleCommandSender object, string f)
2017-08-01 [13:20:08] [Server thread/DEBUG]: #3 src/pocketmine/Server(1920): pocketmine\Server->dispatchCommand(pocketmine\command\ConsoleCommandSender object, string f)
2017-08-01 [13:20:08] [Server thread/DEBUG]: #4 src/pocketmine/Server(2444): pocketmine\Server->checkConsole()
2017-08-01 [13:20:08] [Server thread/DEBUG]: #5 src/pocketmine/Server(2221): pocketmine\Server->tick()
2017-08-01 [13:20:08] [Server thread/DEBUG]: #6 src/pocketmine/Server(2100): pocketmine\Server->tickProcessor()
2017-08-01 [13:20:08] [Server thread/DEBUG]: #7 src/pocketmine/Server(1682): pocketmine\Server->start()
2017-08-01 [13:20:08] [Server thread/DEBUG]: #8 src/pocketmine/PocketMine(511): pocketmine\Server->__construct(BaseClassLoader object, pocketmine\utils\MainLogger object, string phar:///home/fac/PocketMine-MP.phar/, string /home/fac/, string /home/fac/plugins/)
2017-08-01 [13:20:08] [Server thread/DEBUG]: #9 /home/fac/PocketMine-MP.phar(1): require_once(string phar:///home/fac/PocketMine-MP.phar/src/pocketmine/PocketMine.php)