Regexp expression throw an warning when it's not a variable

[arturminchukov]

Describe the bug

To Reproduce

Enter the "kubernetes.pod_name":~"vmlogs.*" in the query input.

Versions of VictoriaLogs datasource and VictoriaLogs backend

datasource version: v0.21.4

Link to dashboard in Victoria Metrics

No response

Please provide dashboard JSON if it is possible

https://play-grafana.victoriametrics.com/explore?schemaVersion=1&panes=%7B%2290y%22:%7B%22datasource%22:%22P566C6523BE02F42C%22,%22queries%22:%5B%7B%22refId%22:%22A%22,%22datasource%22:%7B%22type%22:%22victoriametrics-logs-datasource%22,%22uid%22:%22P566C6523BE02F42C%22%7D,%22editorMode%22:%22code%22,%22expr%22:%22%5C%22kubernetes.pod_name%5C%22:~%5C%22vmlogs.%2A%5C%22%22,%22queryType%22:%22instant%22%7D%5D,%22range%22:%7B%22from%22:%22now-1h%22,%22to%22:%22now%22%7D,%22compact%22:false%7D%7D&orgId=1

Additional information

No response

[arturminchukov]

The fix is now available in v0.22.0. Closing the issue as resolved.