MDL-32683 assert $CFG->slasharguments is enabled in new installs

Thanks Dan Poltawski for spotting it.

lib/tests/outputcomponents_test.php

@@ -120,6 +120,7 @@ class user_picture_testcase extends advanced_testcase {
 
         // verify new install contains expected defaults
         $this->assertEquals('standard', $CFG->theme);
+        $this->assertEquals(1, $CFG->slasharguments);
         $this->assertEquals(1, $CFG->themerev);
         $this->assertEquals(0, $CFG->themedesignermode);
         $this->assertEquals('http://www.example.com/moodle', $CFG->wwwroot);