Fix crash in select method in Decks class

[ShridharGoel]

Purpose / Description

Fix crash in select method in Decks class.

Fixes

Fixes #10046

Approach

Added try-catch block to handle NullPointerException.

Checklist

• You have not changed whitespace unnecessarily (it makes diffs hard to read)
• You have a descriptive commit message with a short title (first line, max 50 chars).
• Your code follows the style of the project (e.g. never omit braces in if statements)
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[mikehardy]

interesting - seems like a reasonable guard

[david-allison]

We should handle the exception here (and ideally add a regression test in a follow up PR).

This is caused by a corrupt collection, we should match Anki Desktop in libAnki code (especially as we lose control of the functionality once the Rust backend is enabled).

We likely want a "corrupt collection" message to appear if a faulty collection is provided.

[david-allison]

Code for a DB error is one of the below. We want to provide the user with options if there is an issue (including check database):

Anki-Android/AnkiDroid/src/main/java/com/ichi2/anki/dialogs/DatabaseErrorDialog.kt

Lines 408 to 422 in 6fd41ae

	const val DIALOG_LOAD_FAILED = 0
	const val DIALOG_DB_ERROR = 1
	const val DIALOG_ERROR_HANDLING = 2
	const val DIALOG_REPAIR_COLLECTION = 3
	const val DIALOG_RESTORE_BACKUP = 4
	const val DIALOG_NEW_COLLECTION = 5
	const val DIALOG_CONFIRM_DATABASE_CHECK = 6
	const val DIALOG_CONFIRM_RESTORE_BACKUP = 7
	const val DIALOG_FULL_SYNC_FROM_SERVER = 8
	/** If the database is locked, all we can do is reset the app */
	const val DIALOG_DB_LOCKED = 9
	/** If the database is at a version higher than what we can currently handle */
	const val INCOMPATIBLE_DB_VERSION = 10

[mikehardy]

LGTM will wait to see if this (much improved...) version where we recognize the corruption looks good to David

[david-allison]

The try/catch doesn't match the stack trace of the issue.

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.ichi2.utils.JSONObject.getString(java.lang.String)' on a null object reference
at com.ichi2.libanki.Decks.select(Decks.java:1)
at com.ichi2.libanki.Decks.current(Decks.java:2)
at com.ichi2.anki.DeckPicker.__renderPage(DeckPicker.java:32)
at com.ichi2.anki.DeckPicker$UpdateDeckListListener.actualOnPostExecute(DeckPicker.java:9)
at com.ichi2.anki.DeckPicker$UpdateDeckListListener.actualOnPostExecute(DeckPicker.java:1)
at com.ichi2.async.TaskListenerWithContext.onPostExecute(TaskListenerWithContext.java:2)
at com.ichi2.async.CollectionTask.onPostExecute(CollectionTask.java:3)
at android.os.AsyncTask.finish(AsyncTask.java:771)
at android.os.AsyncTask.access$900(AsyncTask.java:199)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:788)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:246)
at android.app.ActivityThread.main(ActivityThread.java:8506)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130) 

showDatabaseErrorDialog(DatabaseErrorDialog.DIALOG_DB_ERROR); is broken, and likely has been for some time:

2022-01-02 23:52:14.109 30620-30620/com.ichi2.anki E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.ichi2.anki, PID: 30620
    java.lang.NullPointerException
        at com.ichi2.anki.dialogs.DatabaseErrorDialog.onCreateDialog(DatabaseErrorDialog.kt:92)
        at com.ichi2.anki.dialogs.DatabaseErrorDialog.onCreateDialog(DatabaseErrorDialog.kt:36)
        at androidx.fragment.app.DialogFragment.prepareDialog(DialogFragment.java:647)
        at androidx.fragment.app.DialogFragment.onGetLayoutInflater(DialogFragment.java:561)
        at androidx.fragment.app.Fragment.performGetLayoutInflater(Fragment.java:1698)
        at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:492)
        at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:261)
        at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1840)
        at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1758)
        at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1701)
        at androidx.fragment.app.FragmentManager.executePendingTransactions(FragmentManager.java:564)
        at com.ichi2.anki.AnkiActivity.showDialogFragment(AnkiActivity.java:506)
        at com.ichi2.anki.AnkiActivity.showDialogFragment(AnkiActivity.java:491)
        at com.ichi2.anki.AnkiActivity.showDialogFragment(AnkiActivity.java:487)
        at com.ichi2.anki.AnkiActivity.showAsyncDialogFragment(AnkiActivity.java:531)
        at com.ichi2.anki.AnkiActivity.showAsyncDialogFragment(AnkiActivity.java:517)
        at com.ichi2.anki.DeckPicker.showDatabaseErrorDialog(DeckPicker.java:1319)
        at com.ichi2.anki.DeckPicker$UpdateDeckListListener.actualOnPostExecute(DeckPicker.java:2188)
        at com.ichi2.anki.DeckPicker$UpdateDeckListListener.actualOnPostExecute(DeckPicker.java:2154)
        at com.ichi2.async.TaskListenerWithContext.onPostExecute(TaskListenerWithContext.java:66)
        at com.ichi2.async.CollectionTask.onPostExecute(CollectionTask.java:228)
        at android.os.AsyncTask.finish(AsyncTask.java:771)
        at android.os.AsyncTask.access$900(AsyncTask.java:199)
        at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:788)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7664)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

getCustomView() returned null

We should probably use DIALOG_LOAD_FAILED instead

It'd be useful to get a regression test here: opening a collection, having all the col json columns blank aside from conf

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