Replace == with ===

[JeffPaine]

Fix == comparison at https://github.com/JeffPaine/geojson-topojson/blob/gh-pages/index.html#L142

For some reason, switching it to === causes an error.

[stephanebachelier]

@JeffPaine probably because data can be undefined. And undefined !== null. I have not read your code a lot but it seems data can be undefined when calling merge.

You should use if (!data) instead. undefined and null will evaluate to false.