Tweak addEvent so it silently ignores non-eventing contexts

[jespersm]

I was trying to use a recent QUnit within Rhino (for https://github.com/finnjohnsen/jstest), but couldn't, since the simple context set up in Rhino does not have events, and a very simple 'root' context object.

This tiny change made 1.12.0 usable for my purpose, but it could be that I'm just doing it wrong.

[JamesMGreene]

@Krinkle: I thought we fixed this in Portland...?

Looks like the Travis build failed.

[jespersm]

I didn't try this in the HEAD version, so if you've fixed this since 0.12.0, my apologies.

[JamesMGreene]

@jespersm: Nope, you're in the right. It's still broken in the current mainline.

[Krinkle]

@JamesMGreene Do we want to land another inline detection hack or shall we wait for your nodejs-compat branch to land? Alternatively we could also wait for #405 at which point all browser/html related stuff will be in a code path that doesn't get run under nodejs in the first place.

If the CLA is signed and we squash the broken commit before merging, this is good to go as far as I'm concerned 👍

[JamesMGreene]

I don't mind if this gets landed since I have to totally rebase my PR anyway given the codebase split.

[jzaefferer]

I've made this fix in da6d7cd

@jespersm could you sign our CLA for future contributions? http://contribute.jquery.org/CLA/

FYI @JamesMGreene @Krinkle running node test/node-test.js currently fails, since the require points at the wrong file. Even when fixing the path, the test just does nothing. We should address that.