Fix default values in liquid IAMs

[jennantilla]

Description

One Line Summary

Fix default values in liquid IAMs

Details

Motivation

Bug with In-App Messages where the liquid syntax for tag substitution was showing up in IAMs of users with no tags. String formatting failed when a user has no tags due to trying to format null instead of empty string.

Before:

After:

Scope

In-App Messages

Testing

Unit testing

No unit tests available.

Manual testing

Tested updating the value of userTagsSent to an empty string and the In-App Message displays as expected on Android 12.

Affected code checklist

• Notifications
  • Display
  • Open
  • Push Processing
  • Confirm Deliveries
• Outcomes
• Sessions
• In-App Messaging
• REST API requests
• Public API changes

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
• Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• I have included test coverage for these changes, or explained why they are not needed
• All automated tests pass, or I explained why that is not possible
• I have personally tested this on my device, or explained why that is not possible

Final pass

• Code is as readable as possible.
• I have reviewed this PR myself, ensuring it meets each checklist item

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This change is 

[jkasten2]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @emawby and @nan-li)

[nan-li]

Nice find! If you have an image of the IAM before and after, it'd be great to include in the PR description if we ever look back at this.