fix issue in plugincontroller when loading plugins without info

Author: splitbrain

inc/Extension/PluginController.php

@@ -107,7 +107,7 @@ public function load($type, $name, $new = false, $disabled = false)
             if (!class_exists($class, true)) {
                 # the plugin might be in the wrong directory
                 $inf = confToHash(DOKU_PLUGIN . "$plugin/plugin.info.txt");
-                if ($inf['base'] && $inf['base'] != $plugin) {
+                if (isset($inf['base']) && $inf['base'] != $plugin) {
                     msg(
                         sprintf(
                             "Plugin installed incorrectly. Rename plugin directory '%s' to '%s'.",