Don't assume previous shouldSendCallback exists in RN plugin (fixes #692)

[benvinegar]

cc @marcello3d @nevir @logicalicy @macqueen

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This change is

[benvinegar]

This change will mean that if FATAL_ERROR_KEY is not in data, transmission will only take place if originalCallback exists and returns true (i.e. user-defined callback). Otherwise this will return undefined and transmission will not take place.

I'm not 100% sure if this is the intended behavior or not. Need someone more familiar to chime off on this (@nevir).

[benvinegar]

Re-reading the code, I understand now that this code branch is reached if we're dealing with a non-fatal, in which case we should return true (process the exception) unless an original shouldSend handler is present, in which case we use the return value from that.

[nevir]

Re-reading the code, I understand now that this code branch is reached if we're dealing with a non-fatal, in which case we should return true (process the exception) unless an original shouldSend handler is present, in which case we use the return value from that.

Yup! This looks correct

[benvinegar]

wfm! 3.5.1 going out soon