fix: admin_enqueue_scripts callback should expect a possible null value passed to it

[jasonbahl]

What does this implement/fix? Explain your changes.

This updates the enqueue_admin_assets callback to expect a possible null value for the argument passed from do_action( 'admin_enqueue_scripts' );

Does this close any currently open issues?

closes #180

[josephfusco]

I'm wondering if WP_Error could find it's way into one of these arguments. If so, maybe just removing the typed argument all together? 🤔

[jasonbahl]

@josephfusco ya, maybe 🤔

That's the tricky thing with trying to adhere to code standards but also interacting with a filterable/hookable system like WordPress that doesn't always guarantee things will be what it says they will be 🤔

[jasonbahl]

@josephfusco that said, I'm inclined to think that whatever part of the system (likely a custom plugin or theme) is the culprit that's breaking the "contract" with what the value(s) should be.

WordPress documents that this value should be a string. If it's not a string, something is causing it to not be a string and that something should realistically be what's corrected 🤔

[josephfusco]

@jasonbahl Fair points! Looks good!