fix(gas-adjuster): Do not unwrap in gas-adjuster (#1400)

## What ❔

Do not unwrap in gas-adjuster

## Why ❔

Avoid panics

## Checklist

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- [ ] PR title corresponds to the body of PR (we generate changelog
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- [ ] Tests for the changes have been added / updated.
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core/lib/zksync_core/src/l1_gas_price/gas_adjuster/mod.rs

@@ -97,9 +97,12 @@ impl GasAdjuster {
             )
             .await?;
 
-            METRICS
-                .current_base_fee_per_gas
-                .set(*base_fee_history.last().unwrap());
+            // We shouldn't rely on L1 provider to return consistent results, so we check that we have at least one new sample.
+            if let Some(current_base_fee_per_gas) = base_fee_history.last() {
+                METRICS
+                    .current_base_fee_per_gas
+                    .set(*current_base_fee_per_gas);
+            }
             self.base_fee_statistics.add_samples(&base_fee_history);
 
             if let Some(current_blob_base_fee) = blob_base_fee_history.last() {