message: [GUI] Return early in pollBalanceChanged
  When syncing or reindexing with a pre-existing wallet, there is no need
  to do any updating of the transaction table model data when the chain's
  tip time is prior to the wallet's creation time.
diff: @@ -238,7 +238,14 @@ void WalletModel::pollBalanceChanged()
  if (!lockWallet)
  return;
  - int chainHeight = chainActive.Height();
  + // Don't continue processing if the chain tip time is less than the first
  + // key creation time as there is no need to iterate over the transaction
  + // table model in this case.
  + auto tip = chainActive.Tip();
  + if (tip->GetBlockTime() < getCreationTime())
  + return;
  +
  + int chainHeight = tip->nHeight;
  if (fForceCheckBalanceChanged || chainHeight != cachedNumBlocks) {
  fForceCheckBalanceChanged = false;
  