fillConfigVoids to set default value of empty config options

lib/gnusocial.php

@@ -141,6 +141,7 @@ class GNUsocial
         // Load settings from database; note we need autoload for this
         Config::loadSettings();
 
+        self::fillConfigVoids();
         self::verifyLoadedConfig();
 
         self::initPlugins();
@@ -420,6 +421,14 @@ class GNUsocial
         }
     }
 
+    static function fillConfigVoids()
+    {
+        // special cases on empty configuration options
+        if (!common_config('thumbnail', 'dir')) {
+            common_config_set('thumbnail', 'dir', File::path('thumb'));
+        }
+    }
+
     /**
      * Verify that the loaded config is good. Not complete, but will
      * throw exceptions on common configuration problems I hope.