Prevent crash if multiple YAML files share the same dashid

[Olivier-Sirello_bis]

If multiple YAML files share the same ID, load_yaml() won't return the correct results and fails.
Need to print an error in the log or, better, a warning by taking the first (alphabetical) file

if dash_id_url != "/": yaml_location = ''.join([d["location"] for d in yaml_files if d['dash_id'] == dash_id_url_s]) return yaml_location