fix(event-tags): do not exclude falsy revenue and event values in the event payload

[mikeproeng37]

Summary

• The revenue and event values were excluded from the event object if they evaluated as falsy.
• The fix is to check against null instead of performing a truthy check because the utility method will return null if the revenue or event values cannot be parsed from the tags.

Test plan

• Unit tests and integration tests

[mikeproeng37]

I am running @nchilada's compat suite tests here: https://travis-ci.com/optimizely/fullstack-sdk-compatibility-suite/builds/98673737

[mikeproeng37]

It passes @nchilada's tests here: https://travis-ci.com/optimizely/fullstack-sdk-compatibility-suite/builds/98673737

[aliabbasrizvi]

LGTM

[aliabbasrizvi]

Should we check for undefined?

[mikeproeng37]

Nah because the getRevenueValue function will always return either null or the parsed value

[nchilada]

The most robust (redundant) solution would be to check whether the returned value is a number, but I'm not sure it matters

[coveralls]

Coverage increased (+0.005%) to 97.468% when pulling 827d633 on mng/fix-falsy-event-revenue into d6e6809 on master.

[coveralls]

Coverage increased (+0.005%) to 97.468% when pulling e7ed58a on mng/fix-falsy-event-revenue into d6e6809 on master.

[nchilada]

Thanks for fixing this!

[nchilada]

The most robust (redundant) solution would be to check whether the returned value is a number, but I'm not sure it matters

[nchilada]

Maybe just mention 0 directly? The current test name incorrectly implies that NaN and non-numeric falsy values like '' would also be sent.