[Bug] Cannot read properties of null (reading '_dockerType')

[jamess60]

⚠️ Please verify that this bug has NOT been raised before.

• I checked and didn't find similar issue

🛡️ Security Policy

• I agree to have read this project Security Policy

Description

When creating a monitor with type docker container (polls the docker.sock file) and entering the container name, the monitor turns from green to yellow and this notification is sent via telegram:

Cannot read properties of null (reading '_dockerType')

This is in the uptimekuma container log
2023-10-09T15:21:57+02:00 [MONITOR] WARN: Monitor #30 'Overseer (Plex requests)': Failing: Cannot read properties of null (reading '_dockerType') | Interval: 60 seconds | Type: docker | Down Count: 0 | Resend Interval: 0

The only reference I can find is in #2141 but this was linked to a deprecated feature and marked wontfix.

👟 Reproduction steps

1. Start an uptimekuma:latest container with the docker.sock volume mapped
2. create a monitor for a container on that host using container name instead of ID

👀 Expected behavior

Monitor should be green as the service is up

😓 Actual Behavior

Service is yellow and error is sent to log

🐻 Uptime-Kuma Version

1.21.3

💻 Operating System and Arch

Debian 12 x64

🌐 Browser

Firefox NA

🐋 Docker Version

Docker 24.0.5

🟩 NodeJS Version

No response

📝 Relevant log output

No response

[chakflying]

For the "Docker Host" option in the monitor settings, can you try to select the host again and test that it is working?

Test available when you click on "Edit" under the "Docker Host" option:

[jamess60]

Testing the host works but the issue persists

[chakflying]

You can try to delete and recreate the monitor, which should fix the issue.

The bug here seems to be that the "Docker Host" option is not marked as required, and the data is somehow missing in the monitor config after changes.