What problem does your feature solve?

The stellar ledger entry fetch trustline --asset flag accepts "XLM" (mapped to TrustLineAsset::Native), but trustlines do not hold the native asset — the native balance is held on the account entry itself. Passing --asset xlm silently returns an empty result instead of telling the user the input is invalid:

$ stellar ledger entry fetch trustline --asset xlm --account GB6RQWLXTCVLJZX6LACXVD4WFZHX4YGIPPBSH2YQQMZIMEKA4BM7QLOU
{"entries":[],"latestLedger":61271020}

What would you like to see?

Return an error when "XLM" or "native" is passed as an --asset value, since trustlines cannot hold the native asset. For example:

error: native asset (XLM) does not have a trustline, use `stellar ledger entry fetch account` instead

What alternatives are there?

Leave the behavior as-is, silently returning an empty result.