Agent configuration WOODPECKER_FILTER_LABELS= should not fail

[xoxys]

Component

agent

Describe the bug

Setting WOODPECKER_FILTER_LABELS= in the agent configuration should not fail, but results in:

{"level":"fatal","error":"key '' does not have a value assigned","time":"2024-02-13T13:48:18Z","message":"error running agent"}

System Info

docker.io/woodpeckerci/woodpecker-agent:latest-alpine

Additional context

No response

Validations

• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Checked that the bug isn't fixed in the next version already [https://woodpecker-ci.org/faq#which-version-of-woodpecker-should-i-use]