Fix crash when passing null to clearImmediate

[janicduplessis]

Passing undefined or null to clearImmediate caused apps to crash. It it caused because we try to find the index of the null/undefined timer when we should just do nothing when passed these values.

It is already handled properly in the other Timer functions.

Test plan
Calling clearImmediate with undefined or null should do nothing.

[facebook-github-bot]

By analyzing the blame information on this pull request, we identified @spicyj, @vjeux and @nicklockwood to be potential reviewers.

[vjeux]

@facebook-github-bot shipit

Good catch!

[janicduplessis]

@vjeux I think the bot is sleeping :(

[nicklockwood]

Shouldn't this be !== ? @vjeux

[janicduplessis]

We want != here so it works will null and undefined. It's the same check the is used in other places in this file.

[vjeux]

Actually, it would still crash if you clearImmediate a value that has already been removed.

Could you do

var index = x.indexOf()
if (index !== -1) {
  x.splice()

[facebook-github-bot]

@janicduplessis updated the pull request.

[vjeux]

why do you still check for timer != null? Index === -1 check should catch this no?

[janicduplessis]

I wasn't sure if there could be null values in the immediates array since there was a check for it for the timerID array (https://github.com/janicduplessis/react-native/blob/clear-immediate/Libraries/JavaScriptAppEngine/System/JSTimers/JSTimers.js#L120). I double checked if it was possible and it is not so you are right I can remove the null check.

[facebook-github-bot]

@janicduplessis updated the pull request.

[vjeux]

@facebook-github-bot shipit

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