Fix deprecation warning on PHP 8.1 caused by ltrim
Deprecated function: ltrim(): Passing null to parameter #1 ($string) of type string is deprecated in Drupal\facets_range_datepicker_widget\Plugin\facets\widget\DatepickerWidget->build() (line 72)
Steps to reproduce
Install the module
Create a view and a date range facet
Load the view using the facet
Proposed resolution
Prevent the warning by setting an empty string when the first parameter is null