MDL-31006 fix various notices in PHP54

PHP54 compatibility

lib/moodlelib.php

@@ -1318,7 +1318,7 @@ function get_config($plugin, $name = NULL) {
         if ($localcfg) {
             return (object)$localcfg;
         } else {
-            return null;
+            return new stdClass();
         }
 
     } else {
@@ -1869,6 +1869,7 @@ function make_timestamp($year, $month=1, $day=1, $hour=0, $minute=0, $second=0,
     $totalsecs = abs($totalsecs);
 
     if (!$str) {  // Create the str structure the slow way
+        $str = new stdClass();
         $str->day   = get_string('day');
         $str->days  = get_string('days');
         $str->hour  = get_string('hour');