[Bug] Exit early for budget submission when the wallet is locked

When the wallet is configured for budget submission, an issue arises
where the keypool gets exhausted when the wallet is locked, causing a
crash. This prevents such behavior.

src/budget/budgetmanager.cpp

@@ -165,6 +165,11 @@ uint256 CBudgetManager::SubmitFinalBudget()
  LogPrint(BCLog::MNBUDGET,"%s: Wallet not found\n", __func__);
  return UINT256_ZERO;
  }
+ // Exit if wallet is locked
+ if (vpwallets[0]->IsLocked()) {
+ LogPrint(BCLog::MNBUDGET, "%s: Wallet is locked, can't make collateral transaction.\n", __func__);
+ return UINT256_ZERO;
+ }
  CReserveKey keyChange(vpwallets[0]);
  if (!vpwallets[0]->CreateBudgetFeeTX(wtx, budgetHash, keyChange, BUDGET_FEE_TX)) {
  LogPrint(BCLog::MNBUDGET,"%s: Can't make collateral transaction\n", __func__);