Default src to undefined instead of empty string

[lisamartin00]

These changes resolve #58

[tocker]

Nice catch!
Looks like part of the problem is that the img tag is rendered before calculating the url - we'll need to re-visit this.

[lisamartin00]

Hey @tocker thanks so much for merging this to master - are there plans to publish these changes to npm?

[tocker]

Yes, I'll publish it soon.