Unexpected NaN from sqrt()

[hypcos]

I expected that X.sqrt() should give similar result to X.pow(0.5), but it doesn't.
Especially when the layer is 1.
Example:

> new Decimal(1e-16).pow(0.5)+''
< '1.000000000000002e-8'
> new Decimal(1e-16).sqrt()+''
< 'NaN'
> new Decimal(1e16).neg().pow(0.5)+''
< 'NaN'
> new Decimal(1e16).neg().sqrt()+''
< '99999999.99999979'

[James103]

This is caused by incorrect handling of negative mag in sqrt:

break_eternity.js/break_eternity.js

Lines 2157 to 2158 in 9690197

	} else if (this.layer === 1) {
	return FC(1, 2, Math.log10(this.mag) - 0.3010299956639812);

When layer is 1 and mag is negative, the sqrt function tries to take the logarithm of a negative number, which is NaN.