compatibility with webtrees 2.2

[hartenthaler]

Have you seen the discussion about that principal change from 2.1 to 2.2 in the webtrees forum?

Fatal error in module: family-trees-list
Error: Call to undefined function TreesListModule\app() in /mnt/web109/a3/99/51547399/htdocs/hermann/hartenthaler/php/webtreestest/modules_v4/family-trees-list/module.php:16 Stack trace: #0 /mnt/web109/a3/99/51547399/htdocs/hermann/hartenthaler/php/webtreestest/app/Services/ModuleService.php(722): include()