Player: Fix floating-point errors when float Vector3s are given to sleepOn()

In the future this will change to block positions and the Vector3 issue will cease to be an issue.

Closes #1871

src/pocketmine/Player.php

@@ -1165,6 +1165,7 @@ class Player extends Human implements CommandSender, ChunkLoader, IPlayer{
 			return false;
 		}
 
+		$pos = $pos->floor();
 		$b = $this->level->getBlock($pos);
 
 		$this->server->getPluginManager()->callEvent($ev = new PlayerBedEnterEvent($this, $b));