fix: potential issue for Stage 2

Author: juanmardefago

src/mappings/horizonStaking.ts

@@ -63,7 +63,7 @@ export function handleHorizonStakeWithdrawn(event: HorizonStakeWithdrawn): void
   let id = event.params.serviceProvider.toHexString()
   let indexer = Indexer.load(id)!
   indexer.stakedTokens = indexer.stakedTokens.minus(event.params.tokens)
-  indexer.lockedTokens = indexer.lockedTokens.minus(event.params.tokens)
+  indexer.lockedTokens = BigInt.fromI32(0) // set to 0 to prevent issues when Stage 2 comes
   indexer.tokensLockedUntil = 0 // always set to 0 when withdrawn
   indexer = updateAdvancedIndexerMetrics(indexer as Indexer)
   indexer = calculateCapacities(indexer as Indexer)