Do not blanket-ban all inventory transactions in spectator mode, fixes #2627

instead, we cancel the appropriate events before they are called, so that plugins can uncancel them if they choose.

src/pocketmine/item/Bow.php

@@ -83,7 +83,7 @@ class Bow extends Tool{
 			}
 			$ev = new EntityShootBowEvent($player, $this, $entity, $baseForce * 3);
 
-			if($baseForce < 0.1 or $diff < 5){
+			if($baseForce < 0.1 or $diff < 5 or $player->isSpectator()){
 				$ev->setCancelled();
 			}