Do you want to request a feature or report a bug?
bug

What is the current behavior?
If you have a null data property called 'url', the library has internal errors.

Just try this:

Raven.captureMessage('Installation referral url received.', {
  level: 'info',
  tags: { installationReferralUrl: true },
  extra: { url: null },
})

The exception comes from:
https://github.com/getsentry/raven-js/blob/master/src/raven.js#L1609

Just put a check for a null value or modify truncate to return empty string for null values

What is the expected behavior?
It will not have said error.

React Native, raven-js v3.13.1