[hotfix] warning for conditional

[hamirmahal]

What is the purpose of the change

This pull request fixes a GitHub Actions conditional expression in .github/workflows/template.flink-ci.yml so the comparison against an empty string is evaluated inside the ${{ }} expression.

In .github/workflows/ci.yml (Line: 33, Col: 11): Error from called workflow apache/flink/.github/workflows/template.flink-ci.yml@74a3243984d23a19d1e6ac77c86d1a6c477da584 (Line: 279, Col: 13): Conditional expression contains literal text outside replacement tokens. This will cause the expression to always evaluate to truthy. Did you mean to put the entire expression inside ${{ }}?

https://github.com/apache/flink/actions/runs/22965038052/workflow#L33

Brief change log

• Move the != '' comparison inside the ${{ }} expression in .github/workflows/template.flink-ci.yml

Verifying this change

All pull request checks passed when I ran these changes on my fork.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[flinkbot]

CI report:

• ce3136f Azure: SUCCESS

Bot commands

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• @flinkbot run azure re-run the last Azure build

[davidradl]

nit: could you change the title prefix to [hotfix] as per the process. Otherwise looks good

[hamirmahal]

Sure, I can do that right now.