Curent implementation of Poco::Var operator == throws exception
if "this" object is non empty and "other" object is empty

bool Var::operator == (const Var& other) const
{
if (isEmpty() && !other.isEmpty()) return false;
if (isEmpty() && other.isEmpty()) return true;
return convertstd::string() == other.convertstd::string();
}

There is missing line
if (!isEmpty() && other.isEmpty()) return false;