fix sorting by block number on transactions page

ui/txs/sortTxs.ts

@@ -13,6 +13,12 @@ export default function sortTxs(sorting: TransactionsSortingValue | undefined) {
         return compareBns(tx2.fee.value || 0, tx1.fee.value || 0);
       case 'fee-asc':
         return compareBns(tx1.fee.value || 0, tx2.fee.value || 0);
+      case 'block_number-asc': {
+        if (tx1.block_number && tx2.block_number) {
+          return tx1.block_number - tx2.block_number;
+        }
+        return 0;
+      }
       default:
         return 0;
     }

ui/txs/useTxsSort.tsx

@@ -15,6 +15,7 @@ export const SORT_OPTIONS: Array<SelectOption<TransactionsSortingValue>> = [
   { label: 'Value descending', value: 'value-desc' },
   { label: 'Fee ascending', value: 'fee-asc' },
   { label: 'Fee descending', value: 'fee-desc' },
+  { label: 'Block number ascending', value: 'block_number-asc' },
 ];
 
 type SortingValue = TransactionsSortingValue | undefined;