Fix possible foreach on null errors

lib/Pico.php

@@ -812,6 +812,7 @@ class Pico
         $content = str_replace('%theme_url%', $themeUrl, $content);
 
         // replace %meta.*%
+        if (!empty($this->meta)) {
             $metaKeys = $metaValues = array();
             foreach ($this->meta as $metaKey => $metaValue) {
                 if (is_scalar($metaValue) || ($metaValue === null)) {
@@ -820,6 +821,7 @@ class Pico
                 }
             }
             $content = str_replace($metaKeys, $metaValues, $content);
+        }
 
         return $content;
     }
@@ -1240,6 +1242,7 @@ class Pico
      */
     protected function triggerEvent($eventName, array $params = array())
     {
+        if (!empty($this->plugins)) {
             foreach ($this->plugins as $plugin) {
                 // only trigger events for plugins that implement PicoPluginInterface
                 // deprecated events (plugins for Pico 0.9 and older) will be
@@ -1249,4 +1252,5 @@ class Pico
                 }
             }
         }
+    }
 }