This is related to the current development in
story #9090.
The tracker plugin try to access a function in fusionforge compat plugin directly so when it is not loaded a fatal error is thrown.
Stack trace:
PHP Fatal error: Call to undefined function util_make_base_url() in /usr/share/tuleap/plugins/tracker/include/Tracker/Tracker.class.php on line 1269
PHP 1. {main}() /usr/share/tuleap/plugins/tracker/www/index.php:0
PHP 2. TrackerManager->process() /usr/share/tuleap/plugins/tracker/www/index.php:33
PHP 3. TrackerManager->processSubElement() /usr/share/tuleap/plugins/tracker/include/Tracker/TrackerManager.class.php:127
PHP 4. Tracker->process() /usr/share/tuleap/plugins/tracker/include/Tracker/TrackerManager.class.php:110
PHP 5. Tracker->displayAdmin() /usr/share/tuleap/plugins/tracker/include/Tracker/Tracker.class.php:505
PHP 6. Tracker->displayAdminHeader() /usr/share/tuleap/plugins/tracker/include/Tracker/Tracker.class.php:1458
PHP 7. Tracker->getWarningForDeprecatedFields() /usr/share/tuleap/plugins/tracker/include/Tracker/Tracker.class.php:1450