fix(Utils): add guard against null rule value in validateRule

[afsuyadi]

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Changes

Contributes to #7536

1. Error happens when CreateSegment component is trying to call method validateRule() by passing an object.
2. The method crashes when split() method is executed on a variable that isn't string-type.
3. Inside method validateRule(), only value prop that is accessed and doesn't have its own guard, so the method crashes when it's empty (either null or undefined).
4. I add loose equality guard, to catch only null and undefined value.

How did you test this code?

1. I try to simulate this on my local by manually creating the Segment via UI, but it seems no error happens, because the button Create Segment itself is already been greyed out.
2. I deduce that this error happens via API backend hit.

Screencast.from.14-06-26.11.46.58.webm

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[Zaimwa9]

Thanks for the contribution.
It would be preferable to avoid loosy comparisons if you don't mind.
We have been ramping up on using unit tests on the frontend. validateRule would be a perfect candidate if we could add a couple of parametrized tests around it, including ones validating the fix.
👍

[Zaimwa9]

Actually, let's avoid the loose comparison and keep the !rule.value. From the above (Regex), it hasn't generated an error so there is no reason for now to make a change there

[afsuyadi]

Okay I'll revert the change. Thanks for the review