Automation script Schedule PM with Data Explorer results not sending PMs

As for me, it seems I can’t get a successful trigger of this automation script, whatever the data explorer query is. For example:

SELECT username from users
LIMIT 10

Error 500 when I manually trigger from Automation:

Message (3 copies reported)

TypeError (Nil is not a valid JSON source.)
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