When you try to create a new document via the docman UI you encounter a crash that prevents you to create the document.
Issue has been introduced by 
git #tuleap/stable/ffeb79980253463859ab8fc55b2070c4e29658af (
story #12452).
Trace:
Fatal error: Uncaught TypeError: Argument 1 passed to Docman_Item::accept() must implement interface Tuleap\Docman\Item\ItemVisitor, instance of Docman_View_GetFieldsVisitor given, called in /usr/share/tuleap/plugins/docman/include/view/Docman_View_New.class.php on line 107 and defined in /usr/share/tuleap/plugins/docman/include/Docman_Item.class.php on line 229
TypeError: Argument 1 passed to Docman_Item::accept() must implement interface Tuleap\Docman\Item\ItemVisitor, instance of Docman_View_GetFieldsVisitor given, called in /usr/share/tuleap/plugins/docman/include/view/Docman_View_New.class.php on line 107 in /usr/share/tuleap/plugins/docman/include/Docman_Item.class.php on line 229
Call Stack
#	Time	Memory	Function	Location
1	0.0000	406016	{main}( )	.../index.php:0
2	0.0077	2467728	Tuleap\Request\FrontRouter->route( )	.../index.php:46
3	0.0092	2588064	Tuleap\Request\FrontRouter->routeHandler( )	.../FrontRouter.php:101
4	0.0256	3863256	Tuleap\Docman\DocmanLegacyController->process( )	.../FrontRouter.php:232
5	0.0311	4227232	Tuleap\Docman\ExternalLinks\DocmanHTTPControllerProxy->process( )	.../DocmanLegacyController.php:69
6	0.0325	4241032	Docman_HTTPController->process( )	.../DocmanHTTPControllerProxy.php:65
7	0.0558	4653040	Docman_HTTPController->viewsManagement( )	.../Controler.class.php:64
8	0.0560	4659200	Docman_View_NewDocument->display( )	.../Docman_Controller.class.php:1758
9	0.1362	7325648	Docman_View_NewDocument->_content( )	.../Docman_View_View.class.php:55
10	0.1530	7614168	Docman_View_NewDocument->_getGeneralPropertiesFieldset( )	.../Docman_View_New.class.php:221
11	0.1531	7614248	Docman_View_NewDocument->_getGeneralProperties( )	.../Docman_View_New.class.php:123
12	0.1531	7614248	Docman_View_NewDocument->_getPropertiesFields( )	.../Docman_View_New.class.php:113
13	0.1539	7686104	Docman_Document->accept( )	.../Docman_View_New.class.php:107