Blueprint Message malformed

Configuration Blueprints
1

In my first attempt to create a blueprint, I want to simplify sending MQTT binary messages. If the HA button sends ‘on’ the payload “On” should be sent to the specified MQTT topic. I however get this message:

Message malformed: expected str for dictionary value @ data['action'][0]['if'][0]['state']

As far as I can see, the provided entry IS a string. What am I doing wrong?

blueprint:
    name: Control MQTT binary switches
    domain: automation
    description: Blueprint to automate switching binary MQTT devices
    input:
      light_switch:
        name: Wall switch or HA button
        selector:
          entity:
            domain: 
              - light
              - switch
      target_light:
        name: Device to be switched (MQTT topic)
      command_on:
        name: Command to send to switch ON
        selector:
            text:
                type: text
        default: "On"
      command_off:
        name: Command to send to switch OFF
        selector:
            text:
                type: text
        default: "Off"
 
mode: single
      
trigger:
  - platform: state
    entity_id: !input light_switch
condition: []
action:
  - if:
      - condition: state
        entity_id: !input light_switch
        state: "on"
    then:
      - service: mqtt.publish
        data:
          qos: 0
          retain: false
          topic: !input target_light
          payload: !input command_on
  - if:
      - condition: state
        entity_id: !input light_switch
        state: "off"
    then:
      - service: mqtt.publish
        data:
          qos: 0
          retain: false
          topic: !input target_light
          payload: !input command_off
2

You can’t have multiple if statements at the same level. In this case you can use if-then-else, otherwise for deeper nesting you need to use a choose statement.
Script Syntax - Home Assistant.

If this suggestion solves your problem, please consider clicking the solution button to close the thread.

3

Unfortunately this did not solve the problem. Same error after changing into if-then-else construct.

EDIT:
Actually both options worked after all. I failed to reload the yaml configrations in Developer Tools. After reloading the error disappered and both options (2x if statement AND if-then-else) actually work

@Sir_Goodenough thanks for taking the time to reply and apologies for my ignorance