check existence of clipboard in navigator

[arkamar]

This fixes an issue I have encountered recently in Github webpage in my web browser, where clipboard is not defined in navigator. I believe its presence should be checked before touching its items in similar fashion like other isSupported methods do. This PR is related to #18.

[keithamus]

Thanks for catching this!

[arkamar]

Btw, following error is rapidly popping up (thousands within seconds) in current github webpage:

[Error] Unhandled Promise Rejection: TypeError: undefined is not an object (evaluating 'navigator.clipboard.read')
	K (vendors-node_modules_stacktrace-parser_dist_stack-trace-parser_esm_js-node_modules_github_bro-327bbf-0aaeb22dd2a5.js:1:8117)
	every
	(anonymous function) (environment-e059fd03252f.js:1:5328)
	m (environment-e059fd03252f.js:1:5291)
	(anonymous function) (environment-e059fd03252f.js:1:4196)
	(anonymous function)

It wasn't hard to catch :) It was way harder to find this repo :)

[keithamus]

We'll also need to guard against this in the other methods- isPolyfilled and apply should check navigator.clipboard exists.

[arkamar]

Ah, I see, I didn't realize that when I was comparing it with src/promise-any.ts. I'll work on it.

[arkamar]

I addressed it somehow...

[dylex]

Glad to see this is fixed -- just tracked it down myself. I think this is what's causing github to be slow and have very high CPU use whenever it's open. Any idea when it's getting into production?

[arkamar]

@dylex yes, this exactly what I am experiencing, very high CPU use, lots of exceptions.