[account.cpp] log warnings if acct==nullptr instead of returning early

calling these functions with acct==nullptr should indicate bad code.

libgnucash/engine/Account.cpp

@@ -3904,7 +3904,8 @@ xaccAccountGetNoclosingBalanceChangeInCurrencyForPeriod (Account *acc, time64 t1
 const SplitsVec
 xaccAccountGetSplits (const Account *account)
 {
- return GNC_IS_ACCOUNT(account) ? GET_PRIVATE(account)->splits : SplitsVec{};
+ g_return_val_if_fail (GNC_IS_ACCOUNT(account), SplitsVec{});
+ return GET_PRIVATE(account)->splits;
 }
 
 SplitList *
@@ -3919,6 +3920,7 @@ xaccAccountGetSplitList (const Account *acc)
 size_t
 xaccAccountGetSplitsSize (const Account *account)
 {
+ g_return_val_if_fail (GNC_IS_ACCOUNT(account), 0);
  return GNC_IS_ACCOUNT(account) ? GET_PRIVATE(account)->splits.size() : 0;
 }
 
@@ -3994,12 +3996,14 @@ xaccAccountForEachLot(const Account *acc,
 gboolean
 xaccAccountGetTaxRelated (const Account *acc)
 {
+ g_return_val_if_fail(GNC_IS_ACCOUNT(acc), false);
  return get_kvp_boolean_path(acc, {"tax-related"});
 }
 
 void
 xaccAccountSetTaxRelated (Account *acc, gboolean tax_related)
 {
+ g_return_if_fail(GNC_IS_ACCOUNT(acc));
  set_kvp_boolean_path(acc, {"tax-related"}, tax_related);
 }
 
@@ -4013,6 +4017,7 @@ xaccAccountGetTaxUSCode (const Account *acc)
 void
 xaccAccountSetTaxUSCode (Account *acc, const char *code)
 {
+ g_return_if_fail(GNC_IS_ACCOUNT(acc));
  set_kvp_string_path (acc, {"tax-US", "code"}, code);
 }
 
@@ -4102,6 +4107,7 @@ xaccAccountSetAppendText (Account *acc, gboolean val)
 gboolean
 xaccAccountGetIsOpeningBalance (const Account *acc)
 {
+ g_return_val_if_fail (GNC_IS_ACCOUNT(acc), false);
  if (GET_PRIVATE(acc)->type != ACCT_TYPE_EQUITY)
  return false;
 
@@ -4111,6 +4117,7 @@ xaccAccountGetIsOpeningBalance (const Account *acc)
 void
 xaccAccountSetIsOpeningBalance (Account *acc, gboolean val)
 {
+ g_return_if_fail (GNC_IS_ACCOUNT(acc));
  if (GET_PRIVATE(acc)->type != ACCT_TYPE_EQUITY)
  return;
  set_kvp_string_path(acc, {"equity-type"}, val ? "opening-balance" : nullptr);