fix: currentCard not initialized

[BrayanDSO]

Fixes

https://forums.ankiweb.net/t/what-does-this-error-mean/44915

Approach

Initialize the variable instead of depending of lateinit

How Has This Been Tested?

Opened the templatePreviewer with Don't keep activities on + the current unit tests

Learning (optional, can help others)

Don't trust any lateinit

Checklist

Please, go through these checks before submitting the PR.

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• [X ] You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[david-allison]

Thanks!

[lukstbit]

Ok.
Based on the linked forum discussion I'm tagging this to be cherry picked.