Fix some random NullPointerExceptions

[Stypox]

What is it?

• Bugfix (user facing)
• Feature (user facing)
• Codebase improvement (dev facing)
• Meta improvement to the project (dev facing)

Description of the changes in your PR

I got a random NullPointerException when clicking fast on the search button, this PR should prevent it, even though it should never happen.
While I was at it I also fixed two other random NPEs.

    java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object java.util.Map.get(java.lang.Object)' on a null object reference
        at org.schabi.newpipe.fragments.list.search.SearchFragment.onOptionsItemSelected(SearchFragment.java:460)
        at androidx.fragment.app.Fragment.performOptionsItemSelected(Fragment.java:2830)
        ...

Fixes the following issue(s)

• Fixes UI Crash (minor bug) : Simultaneously open menus in Settings #5587
• Fixes Crash when opening very quickly the search window after NewPipe launch #5812

APK testing

On the website the APK can be found by going to the "Checks" tab below the title and then on "artifacts" on the right.

Due diligence

• I read the contribution guidelines.

[Stypox]

@XiangRongLin done