apexcharts-card: "color_threshold" + "type: line" broken in v1.7.0?

Checklist

• I updated the card to the latest version available
• I cleared the cache of my browser
• I verified that I’m really running the lastest version in my browser console
• I checked if there is another issue opened with the same problem

Describe the bug (Thank you very much for this very useful card!) The problem:

• “color_threshold” and “type: line” draws nothing in version 1.7.0. It worked before I updated to 1.7.0.
• “color_threshold” and “type: column” draws as expected in version 1.7.0

Version of the card Version: 1.7.0

To Reproduce

These are the two configuration I used, fetched from the documentation example:

Broken:

type: 'custom:apexcharts-card'
experimental:
  color_threshold: true
series:
  - entity: sensor.fake_temperature
    type: line
    color_threshold:
      - value: -10
        color: blue
        opacity: 1
      - value: 0
        color: cyan
      - value: 15
        color: green
      - value: 25
        color: orange

Works:

type: 'custom:apexcharts-card'
experimental:
  color_threshold: true
series:
  - entity: sensor.fake_temperature
    type: column
    color_threshold:
      - value: -10
        color: blue
        opacity: 1
      - value: 0
        color: cyan
      - value: 15
        color: green
      - value: 25
        color: orange

Screenshot: Works:

Screenshot: Broken:

Expected behavior The documentation used the above yaml to describe an example on how to use color_threshold (I only changed the entity). It worked on the previous version (1.6.x?).

Desktop (please complete the following information):

• Vivaldi 3.6.2165.36 (Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.151 Safari/537.36)
• Firefox 85.0.2 (Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:85.0) Gecko/20100101 Firefox/85.0)

Smartphone (please complete the following information): N/A

Additional context Add any other context about the problem here.