expected invalid equals logic

[rusefillc]

		// If both are invalid, they are equal
		if (!Valid && !other.Valid) {
			return true;
		}

as opposed to https://stackoverflow.com/questions/1565164/what-is-the-rationale-for-all-comparisons-returning-false-for-ieee754-nan-values

[dron0gus]

#35
This will need minor fixes of some unit tests, where compare against unexpected is used.
Short grepping through firmware code shows no such compares in code. But careful review is needed.