Use correct fix for nextPage being null while creating error report

[TobiGr]

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

#12408 does not fix the underlying issue but tries to handle the symptoms. nextPage cannot be null when handleNextItems() is called, because at that point there is a page that was fetched.
#12408 made it so that is unlikely that error reports are generated. When there was an ExtractionException it is likely that there is no nextPage. The issue is that nextPage is reassigned before generating the error report.

APK testing

The APK can be found by going to the "Checks" tab below the title. On the left pane, click on "CI", scroll down to "artifacts" and click "app" to download the zip file which contains the debug APK of this PR. You can find more info and a video demonstration on this wiki page.

Due diligence

• I read the contribution guidelines.

[koukibadr]

@TobiGr
#12408 does fix the pagination error crash, handleNextItems is called whenever there's a fetch for new data the fix was adding an assert to the page object when it's retrieved using nextPage = result.getNextPage(); so newPage could be null in this stage.
With this PR the retrieval of newPage is done after the assertion if so it won't be null, thisPR and #12408 are two possible fix solutions for the same bug.

[Stypox]

We should still report the error if nextPage == null, I pushed a commit to do that. Thanks!