Error with Moodle 2.6.1

[maxCSA]

Hi,
I get the following error with Moodle 2.6.1:

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Missing firstnamephonetic property in $user object, this is a performance problem that needs to be fixed by a developer. Please use user_picture::fields() to get the full list of required fields.

line 196 of /lib/outputcomponents.php: call to debugging()
line 2254 of /lib/outputrenderers.php: call to user_picture->__construct()
line 81 of /blocks/mymentees/block_mymentees.php: call to core_renderer->user_picture()
line 296 of /blocks/moodleblock.class.php: call to block_mymentees->get_content()
line 238 of /blocks/moodleblock.class.php: call to block_base->formatted_contents()
line 956 of /lib/blocklib.php: call to block_base->get_content_for_output()
line 1008 of /lib/blocklib.php: call to block_manager->create_block_contents()
line 353 of /lib/blocklib.php: call to block_manager->ensure_content_created()
line 26 of /theme/essential/layout/frontpage.php: call to block_manager->region_has_content()
line 870 of /lib/outputrenderers.php: call to include()
line 800 of /lib/outputrenderers.php: call to core_renderer->render_page_layout()
line 101 of /index.php: call to core_renderer->header()

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