Bugfixed gpio, improved bitmap example script

lib/GpioPin.php

@@ -76,7 +76,9 @@ class GpioPin
     
     public function __destruct()
     {
-        fclose($this->fd);
+    	if ($this->fd) {
+	        fclose($this->fd);
+	    }
     }
     
     public function setDirection($direction)