Errant Behavior When Hiding Currently Selected Category

[rhsalas3]

Description

We should handle the use case of when a user hides/deletes the category they had currently selected on the main screen.

This issue was also found on iOS, and fixed in willowtreeapps/vocable-ios#477

Steps To Reproduce:

1. Launch the app
2. On the mains screen, navigate to a category
3. Assuming the category you've selected is 'Basic Needs'...
4. Open Settings > Categories and Phrases and hide the 'Basic Needs' category
   • This is done by tapping the 'eye' icon so that it no longer has a slash through it.
5. Return to the main screen

Expected behavior
Using the 'Basic Needs' category as our example, hiding the category should result in 'Personal Care' becoming the second category listed on the Categories and Phrases screen. The 4th category listed should now be 'Environment'. Therefore, when I return to the Main screen, the app should automatically be updated to display 'Personal Care' as the selected category; with that category's phrases.

Actual Behavior
Considering the scenario already described in the Expected Behavior section: the category displayed on the Main screen ends up being 'Environment' (whatever category is listed in that 4th slot on the Categories and Phrases screen) instead of 'Personal Care'. The category is not automatically selected. And the phrases displayed belong to the category that was hidden; the 'Basic Needs' category's phrases, to follow our example.

Screenshots/Recordings
Here is a recording of the behavior described, using the 'Basic Needs' category as the example.

VocableAndroid_hidingSelectedCategory_resultsInErrantBehavior.mov

Smartphone:

• Device: Pixel 5 (emulator)
• OS: Android 12