fix: fix incorrect string comparison in OPERATOR_ADDRESS check

[hexcow]

Description

I noticed a bug in the script where -eq was used to check if OPERATOR_ADDRESS is empty. Since -eq is for numeric comparisons, this caused an error:

bash: [: "" -eq: unary operator expected

I fixed it by replacing -eq "" with -z, which correctly checks for an empty string.

Type of change

Please delete options that are not relevant.

• New feature
• Bug fix
• Optimization
• Refactor

Checklist

• “Hotfix” to testnet, everything else to staging
• Linked to Github Issue
• This change depends on code or research by an external entity
  • Acknowledgements were updated to give credit
• Unit tests added
• This change requires new documentation.
  • Documentation has been added/updated.
• This change is an Optimization
  • Benchmarks added/run
• Has a known issue
  • Link to the open issue addressing it
• If your PR changes the Operator compatibility (Ex: Upgrade prover versions)
  • This PR adds compatibility for operator for both versions and do not change batcher/docs/examples
  • This PR updates batcher and docs/examples to the newer version. This requires the operator are already updated to be compatible

p.s. Everything works as expected now 🚀

[Mechanix97]

Opened issue #1853

[Mechanix97]

Also opened PR #1854 with more script fixings
Thanks @hexcow!

[MauroToscano]

Thanks for reporting the issue, we have solved it along with others similar checks