Prevents package from crashing when import.meta.url is undefined

[IronGeek]

This PR prevents open from crashing when the package is bundled for non-ESM format.
It does so by adding a simple truthy guard for import.meta.url before passing it to fileURLToPath() function.

In non-ESM context, import.meta.url is undefined.

open/index.js

Lines 13 to 15 in 36c61af

	// Path to included `xdg-open`.
	const __dirname = path.dirname(fileURLToPath(import.meta.url));
	const localXdgOpenPath = path.join(__dirname, 'xdg-open');

And since fileURLToPath() does not accept undefined value as argument, it will throw the following error:

node:internal/url:1210
    throw new ERR_INVALID_ARG_TYPE('path', ['string', 'URL'], path);
    ^

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string or an instance of URL. Received undefined
...

[sindresorhus]

This should be opened on the bundler you use instead. It's up to your bundle to polyfill things if it converts from ESM to non-ESM.