Hide "We are indexing this chain right now. Some of the counts may be inaccurate" banner if no txs in blockchain

[vbaranov]

Motivation

Blokcscout shows " n% Blocks Indexed - We're indexing this chain right now. Some of the counts may be inaccurate." banner at the top even if blockchain doesn't have transactions

Changelog

Enhancements

If there are no transactions in the blockchain, the banner is hidden

Checklist for your Pull Request (PR)

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so by submitting a PR to https://github.com/blockscout/docs
• If I added/changed/removed ENV var, I submitted a PR to https://github.com/blockscout/docs to update the list of env vars at https://github.com/blockscout/docs/blob/master/for-developers/information-and-settings/env-variables.md and I updated the version to master in the Version column. Changes will be reflected in this table: https://docs.blockscout.com/for-developers/information-and-settings/env-variables.
• If I add new indices into DB, I checked, that they are not redundant with PGHero or other tools

[coveralls]

Pull Request Test Coverage Report for Build af0147d1-d895-44fd-91d1-da759083307f

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 76.922%

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Totals
Change from base Build ddd4c339-6780-406f-94a1-6f24040565a1:	0.2%
Covered Lines:	5293
Relevant Lines:	6881

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💛 - Coveralls