Tighten validation on addr when creating from existing address

[alanshaw]

• Throws if addr is falsy value such as 0, false or NaN
• Allows if null, undefined, ''

[vmx]

Could you please add a test case for undefined?

[vmx]

What about:

if (addr == null) {
  addr = ''
}

That seems easier to read for future generations ;)

[vmx]

It took my a while to figure out that == null also matches undefined, I'm just so used to ===. I personally would prefer a if (addr === undefined || addr === null). But that's surely a matter of style/taste, so feel free to leave it with == null.

[alanshaw]

@vmx is good?

[vmx]

Thanks for the quick fixes!