Rule should match if optional action parameters are not specified in payload

/opt/stackstorm/packs/my_application/actions/deploy.yaml

---
name: 'deploy'
description: 'Workflow to deploy an application'
runner_type: 'mistral-v2'
entry_point: 'workflows/deploy.yaml'
enabled: true
parameters:
  repo_url:
    description: The repository URL of the (compiled) application
    required: true
    position: 0
  server_application:
    description: The application/purpose of a server to deploy this application to
    required: true
    position: 1
  server_role:
    description: The role of a server to deploy this application to. Possible values are "tomcat", "apache", "postgres", "rabbitmq", etc
    required: true
    position: 2
  server_environment:
    description: The environment of a server to deploy this application to. Possible values are "prd", "acc", "tst" or "dev"
    required: true
    position: 3
  target_dir:
    description: The target directory for the application code
    position: 4
  pre_update_command:
    description: 'This command is executed locally before code is updated'
    position: 5
  post_update_command:
    description: 'This command is executed locally after code is updated'
    position: 6

/opt/stackstorm/packs/my_application/triggers/deploytrigger.yaml

---
name: deploytrigger
description: 'Application deployment trigger.'

/opt/stackstorm/packs/my_application/rules/deploy.yaml

---
name: deploy
description: "Deployment rule that can be called for an application deployment from Jenkins or something similar."
enabled: true

trigger:
  type: my_application.deploytrigger

action:
  ref: "my_application.deploy"
  parameters:
    repo_url: "{{trigger.repo_url}}"
    server_application: "{{trigger.server_application}}"
    server_role: "{{trigger.server_role}}"
    server_environment: "{{trigger.server_environment}}"
    target_dir: "{{trigger.target_dir}}"
    pre_update_command: "{{trigger.pre_update_command}}"
    post_update_command: "{{trigger.post_update_command}}"

/tmp/trigger-instance.yaml

---
trigger: "my_application.deploytrigger"
payload:
  repo_url: "ssh://git@bitbucket.org/my/helloworldapp.git"
  server_application: "shared"
  server_role: "apache"
  server_environment: "tst"
  target_dir: "/srv/helloworldapp"
  pre_update_command: ~
  post_update_command: ~

A rule DOES match if I run the rule tester with all the workflow/action parameters defined in the trigger instance payload:

st2-rule-tester --config-file /etc/st2/st2.conf --rule=/opt/stackstorm/packs/my_application/rules/deploy.yaml --trigger-instance=/tmp/trigger-instance.yaml --debug --verbose

However if I DON'T specify the optional workflow parameters "target_dir", "pre_update_command" and "post_update_command" there is NO rule match. It would be nice if optional workflow/action parameters are not required in the trigger payload.