fix callable hooks
diff --git a/system/core/Hooks.php b/system/core/Hooks.php
index 767dc4c..fde43d0 100644
--- a/system/core/Hooks.php
+++ b/system/core/Hooks.php
@@ -127,7 +127,7 @@
 			return FALSE;
 		}
 
-		if (isset($this->hooks[$which][0]) && is_array($this->hooks[$which][0]))
+		if (is_array($this->hooks[$which]) && isset($this->hooks[$which][0]) && is_array($this->hooks[$which][0]))
 		{
 			foreach ($this->hooks[$which] as $val)
 			{