Using to_string for scalars causes crashes

[afoolsbag]

In function

units/units/units.cpp

Lines 1723 to 1736 in e5b5765

	std::string to_string(const measurement& measure, std::uint32_t match_flags)
	{
	std::stringstream ss;
	ss.precision(6);
	ss << measure.value();
	ss << ' ';
	auto str = to_string(measure.units(), match_flags);
	if (isNumericalStartCharacter(str.front())) {
	str.insert(str.begin(), '(');
	str.push_back(')');
	}
	ss << str;
	return ss.str();
	}

the call

        auto str = to_string(measure.units(), match_flags);

may return an empty string.

This will cause a crash when using str.front().

[phlptp]

thanks I will look into it

[phlptp]

Fixed, Thanks!