Block gap assumes there is a warp sync even when there isn't any

[nazar-pc]

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• This is not a support question.

Description of bug

When node starts and there is a block gap, warp sync phase is set to DownloadingBlocks:

polkadot-sdk/substrate/client/network/sync/src/strategy/chain_sync.rs

Lines 440 to 443 in 2d3a693

	let warp_sync_progress = self.gap_sync.as_ref().map(|gap_sync| WarpSyncProgress {
	phase: WarpSyncPhase::DownloadingBlocks(gap_sync.best_queued_number),
	total_bytes: 0,
	});

The funny thing is, this happens even if there is no warp sync params configured, meaning warp sync is not present/possible at all.

Steps to reproduce

Happens after inserting a block with higher number using apply_block and restarting node afterwards

[bkchr]

When node starts and there is a block gap

Not wanting to say that the current behavior is correct, but why do you have a gap?

[nazar-pc]

Due to custom sync mechanism, see #4407