Fixes Issue 6436: getString(...) must not be null

[Jason-Whitmore]

Description (required)

Fixes #6436

What changes did you make and why?

The getString() method was changed to allow returning a null value upon failure. This prevents the NPE.

Then, usages of getString() were modified to handle potential null value returns. If getString() returned null and a non null String was required, the empty string was used instead (this can be changed to throw an exception if needed).

Tests performed (required)

Tested ProdDebug on Android Studio Emulator with API level 36.

Reproducing the original issue is tricky, but this is probably the simplest way:

1. Start with no bookmarks or clear all bookmarks
2. Go to Explore
3. Using the search function, find an item which has no images associated with it. I used "Q1687285".
4. Bookmark the item
5. Go to Bookmarks
6. Tap "Categories"

On main, the issue will reproduce with an NPE. On this branch, there will be no crash.

If step 1 is skipped, the app may crash with #6464, but not #6436 according to the logs.

[github-actions]

✅ Generated APK variants!

• 🤖 Download betaDebugAPK
• 🤖 Download prodDebugAPK

[nicolas-raoul]

Following the steps above, I indeed get no crash.

By the way, Bookmarks>Items is empty, any idea why? Locations also empty despite bookmarking a location in Nearby.

[nicolas-raoul]

When skipping step 1 and tapping Bookmarks>Items I get this crash, I guess it is expected too.

APP_VERSION_NAME=6.0.2-debug-Jason-Whitmore-issue_6436
ANDROID_VERSION=16
STACK_TRACE=java.lang.IndexOutOfBoundsException: Empty list doesn't contain element at index 0.
at kotlin.collections.EmptyList.get(Collections.kt:37)
at kotlin.collections.EmptyList.get(Collections.kt:25)
at fr.free.nrw.commons.bookmarks.items.BookmarkItemsDao.convertToCategoryItems(BookmarkItemsDao.kt:182)
at fr.free.nrw.commons.bookmarks.items.BookmarkItemsDao.fromCursor(BookmarkItemsDao.kt:162)
at fr.free.nrw.commons.bookmarks.items.BookmarkItemsDao.getAllBookmarksItems(BookmarkItemsDao.kt:53)
at fr.free.nrw.commons.bookmarks.items.BookmarkItemsController.loadFavoritesItems(BookmarkItemsController.kt:21)
at fr.free.nrw.commons.bookmarks.items.BookmarkItemsFragment.initList(BookmarkItemsFragment.kt:47)
at fr.free.nrw.commons.bookmarks.items.BookmarkItemsFragment.onViewCreated(BookmarkItemsFragment.kt:34)
at androidx.fragment.app.Fragment.performViewCreated(Fragment.java:2987)

[Jason-Whitmore]

Following the steps above, I indeed get no crash.

By the way, Bookmarks>Items is empty, any idea why? Locations also empty despite bookmarking a location in Nearby.

I noticed this too when I was debugging. Interestingly, the method BookmarkItemsFragment.initList will correctly retrieve the list of favorite items as the depictItems list, and hide the You haven't added any bookmarks text, but will not actually display the items to the user.

I'm not sure when the bug first appeared. One possibility is that the bug first appeared when the old Java code was rewritten to Kotlin a few months ago.