fix: use default node url if the user happens to explicitly set []

[gregmagolan]

Corner case I hit in rules_js. The current error message if you accidentally set node_urls = [] is not great. This bit of code restores the default value if the user happens to clear it with an empty list.

[jbedard]

What is the corner case you hit?

Generally "correcting" bad API usage just makes things more complicated imo :/

[gregmagolan]

What is the corner case you hit?

Generally "correcting" bad API usage just makes things more complicated imo :/

The corner case was a wrapper macro. I think the default should be [] personally because that implies that you want to canonical upstream source, however, having the default set to the canonical URL is useful for the doc generator. There is precedent for setting the default within the rule with the node_repositories attribute so this follow a similar pattern. I set the default to [] initially but wasn't happy with the generated docstring with that change.