Dashboard: When creating a new chart with two sources, selecting another color than the default generates an error "UNPROCESSABLE_ENTITY"

[LM1LC3N7]

Describe the bug
When creating a new chart with two sources, selecting another color than the default generates an error "UNPROCESSABLE_ENTITY".

To Reproduce
Steps to reproduce the behavior:

1. Create a new dashboard (or edit one)
2. Add a new chart
3. Add two sources (like two temperature devices)
4. Select colors different than the default selected
5. Click on "save"
6. See error, the page is stuck on "loading"

Expected behavior
Choosing any color should work as expected

Screen Recording
https://github.com/user-attachments/assets/15f95606-7ce7-4c5a-b3ca-abe0dabccd79

Your Gladys installation (please complete the following information):

• Docker
• Official last image v4.50.2

Web browser error

Uncaught (in promise) TypeError: s is undefined
    value apexcharts.common.js:6
    value apexcharts.common.js:6
    value apexcharts.common.js:6
    value apexcharts.common.js:6
    value apexcharts.common.js:14
    value apexcharts.common.js:6
    value apexcharts.common.js:14
    value apexcharts.common.js:14
    c ApexChartComponent.jsx:218
    componentDidMount ApexChartComponent.jsx:222
    Preact 7
    a Chart.jsx:259
    componentDidMount Chart.jsx:290
    Preact 7
    a EditChart.jsx:67
    S Preact

{
  "response": {
    "status": 422,
    "data": {
      "status": 422,
      "code": "UNPROCESSABLE_ENTITY",
      "properties": [
        {
          "message": "\"[2][0].colors[0]\" must be a string",
          "attribute": "boxes",
          "value": [
            [
              {
                "type": "temperature-in-room",
                "room": "salle-de-bain"
              },
              {
                "type": "humidity-in-room",
                "room": "salle-de-bain"
              }
            ],
            [
              {
                "type": "temperature-in-room",
                "room": "salle-de-douche"
              },
              {
                "type": "humidity-in-room",
                "room": "salle-de-douche"
              }
            ],
            [
              {
                "type": "chart",
                "device_feature_names": [
                  "Salle de bain",
                  "Douche"
                ],
                "device_features": [
                  "zigbee2mqtt-sdd-temp-sonoff-temperature-sensor-decimal-temperature",
                  "zigbee2mqtt-sdb-temp-sonoff-temperature-sensor-decimal-temperature"
                ],
                "title": "Salles d'eau",
                "chart_type": "area",
                "colors": [
                  null,
                  "#00cec9"
                ],
                "display_axes": true,
                "display_variation": true,
                "interval": "last-day"
              }
            ]
          ],
          "type": "Validation error"
        }
      ]
    }
  }
}