Fix format of Slack when result is nil

app/models/project_services/slack_slash_commands_service.rb

@@ -16,7 +16,7 @@ class SlackSlashCommandsService < ChatSlashCommandsService
   def trigger(params)
     # Format messages to be Slack-compatible
     super.tap do |result|
-      result[:text] = format(result[:text])
+      result[:text] = format(result[:text]) if result.is_a?(Hash)
     end
   end

spec/models/project_services/slack_slash_commands_service.rb → spec/models/project_services/slack_slash_commands_service_spec.rb

@@ -18,7 +18,8 @@ describe SlackSlashCommandsService, :models do
       let(:service) do
         project.create_slack_slash_commands_service(
-          properties: { token: 'token' }
+          properties: { token: 'token' },
+          active: true
         )
       end