FIX: hook insertExtraFields must return a returnvalue (0,1,-1)

htdocs/core/class/hookmanager.class.php

@@ -131,6 +131,7 @@ class HookManager
         // Define type of hook ('output', 'returnvalue' or 'addreplace'). 'addreplace' should be type for all hooks. 'output' and 'returnvalue' are deprecated.
         $hooktype='output';
         if (preg_match('/^pdf_/',$method)) $hooktype='returnvalue';	// pdf_xxx except pdf_writelinedesc are returnvalue hooks. When there is 2 hooks of this type, only last one win.
+        if ($method =='insertExtraFields') $hooktype='returnvalue';
         if (in_array(
         	$method,
         	array(