Menu error when not assigned

[vyskoczilova]

$menu_3 = $this->menu_repository->get( Plugin::FOOTER_MENU_3 );

The footer menu is not assigned; it returns fatal:

Call to a member function source() on null [search►](https://www.google.com/search?sourceid=tracy&q=Error+Call+to+a+member+function+source%28%29+on+null)
File: [.../gutenberg-kemiex-landing/vendor/wpify/model/src/MenuRepository.php:72](phpstorm://open?file=%2FUsers%2Fmejta%2Fsites%2Fgutenberg-kemiex-landing%2Fvendor%2Fwpify%2Fmodel%2Fsrc%2FMenuRepository.php&line=72)

62:            if ( is_string( $source ) && in_array( $source, array_keys( $this->menu_locations ) ) ) {
63:                $wp_menu = wp_get_nav_menu_object( $this->menu_locations[ $source ] );
64:            }
65:    
66:            if ( $wp_menu ) {
67:                $menu = parent::get( $wp_menu );
68:            } else {
69:                $term = parent::get( $source );
70:                $menu = $term ? new $model_class( $this->manager() ) : null;
71:    
72:                $menu->source( $term->source() );

73:            }
74:    
75:            return $menu;
76:        }

Current solution is check has_nav_menu() before, but you might want to fix it (or I'm not using it the right way)