fix: index-eth-tx cmd fail on empty indexer db

[yihuang]

Solution:

• start from latest height is db is empty
• improve the cmd description.

Closes: #XXX

Description

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[yihuang]

@facs95 this PR should fix the issue you mentioned before.

[facs95]

Thanks for taking care of this! 🙏

[yihuang]

integration test passed after rerun.