message: Assume presence of immediate caller in call site.
  This change does not require check of the front element considering that
  call stack is consistent.
diff: @@ -3675,28 +3675,9 @@ where
  let immediate_caller = match self.get_immediate_caller() {
  Some(call_stack_element) => call_stack_element,
  None => {
  - // Empty call stack is strictly a programming error.
  - // A Runtime can't be created with empty call stack or with a stored variant as
  - // first as the constructor is guarded with debug assertions.
  - match self.call_stack().first() {
  - Some(CallStackElement::Session { account_hash }) => {
  - // For example the genesis process originates with a session code started by
  - // a system account.
  - return Ok(account_hash == &PublicKey::System.to_account_hash());
  - }
  - Some(
  - CallStackElement::StoredContract { .. }
  - | CallStackElement::StoredSession { .. },
  - )
  - | None => {
  - debug_assert!(
  - false,
  - "First element of the stack should be present and not a stored variant."
  - );
  + // Immediate caller is assumed to exist at a time this check is run.
  return Ok(false);
  }
  - }
  - }
  };
  match immediate_caller {
  