Software error when Elasticsearch is not configured and rake searchindex:rebuild

[martini]

Infos:

• Used Zammad version: 3.5
• Installation method (source, package, ..): any
• Operating system: any
• Database + version: any
• Elasticsearch version: any
• Browser + version: any

Expected behavior:

• Show nice error message if rake searchindex:rebuild is used and no Elasticsearch is configured.

Actual behavior:

• Software error is shown in rake searchindex:rebuild

rake searchindex:rebuild
rake aborted!
NoMethodError: undefined method `split' for nil:NilClass
/home/me/src/zammad/lib/tasks/search_index_es.rake:338:in `es_version_supported?'
/home/me/src/zammad/lib/tasks/search_index_es.rake:183:in `block (2 levels) in <main>'
Tasks: TOP => searchindex:rebuild => searchindex:version_supported
(See full trace by running task with --trace)

Steps to reproduce the behavior:

• zammad run rails r "Setting.set('es_url', '')"
• zammad run rake searchindex:rebuild