El script de automatización Schedule PM con resultados de Data Explorer no envía PMs

Por mi parte, parece que no puedo activar correctamente este script de automatización, sin importar la consulta del explorador de datos. Por ejemplo:

SELECT username from users
LIMIT 10

Error 500 cuando lo activo manualmente desde Automatización:

Mensaje (3 copias reportadas)

TypeError (Nil no es una fuente JSON válida.)
app/controllers/application_controller.rb:418:in `block in with_resolved_locale'
app/controllers/application_controller.rb:418:in `with_resolved_locale'
lib/middleware/omniauth_bypass_middleware.rb:74:in `call'
lib/content_security_policy/middleware.rb:12:in `call'
lib/middleware/anonymous_cache.rb:369:in `call'
config/initializers/100-quiet_logger.rb:20:in `call'
config/initializers/100-silence_logger.rb:29:in `call'
lib/middleware/enforce_hostname.rb:24:in `call'
lib/middleware/request_tracker.rb:228:in `call'

Backtrace

plugins/discourse-data-explorer/lib/report_generator.rb:42:in `parse'
plugins/discourse-data-explorer/lib/report_generator.rb:42:in `params_to_hash'
plugins/discourse-data-explorer/lib/report_generator.rb:15:in `generate'
plugins/discourse-data-explorer/plugin.rb:117:in `block (4 levels) in activate!'
plugins/discourse-automation/app/models/discourse_automation/automation.rb:83:in `trigger!'
plugins/discourse-automation/app/controllers/discourse_automation/automations_controller.rb:10:in `trigger'
actionpack (7.0.4.3) lib/action_controller/metal/basic_implicit_render.rb:6:in `send_action'
actionpack (7.0.4.3) lib/abstract_controller/base.rb:215:in `process_action'
actionpack (7.0.4.3) lib/action_controller/metal/rendering.rb:53:in `process_action'
actionpack (7.0.4.3) lib/abstract_controller/callbacks.rb:234:in `block in process_action'

Env

HTTP HOSTS: discourse.canapin.dev