JetBrains: Fix errors when loading with no prior search saved

Created by: philipp-spiess

This fixes an issue that we're seeing whenever someone is testing the extension for the first time.

The problem here is that we used to return an object for the previous search consistent of a lot of null values. E.g. query: null. The JS code however expects the value to be null or a valid LastSearch type.

I've made changes to properly handle null in the bridge and return null in the case that there is no last search.

Test plan

https://www.loom.com/share/6f05c9c6bbe14af18aa584c3fe06bc3e

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.