fix several potential crashes

src/Kp2aBusinessLogic/database/CheckDatabaseForChanges.cs

@@ -30,7 +30,6 @@ namespace keepass2android
 {
   public class CheckDatabaseForChanges : OperationWithFinishHandler
   {
-    private readonly Context _context;
     private readonly IKp2aApp _app;
 
 
@@ -66,7 +65,7 @@ public override void Run()
 
           if (!MemUtil.ArraysEqual(_app.CurrentDb.KpDatabase.HashOfFileOnDisk, hashingRemoteStream.Hash))
           {
-            _app.TriggerReload(_context, null);
+            _app.TriggerReload(null, null);
             Finish(true);
           }
           else

src/java/KP2ASoftkeyboard_AS/app/src/main/java/keepass2android/softkeyboard/KP2AKeyboard.java

@@ -521,13 +521,15 @@ public void onConfigurationChanged(Configuration conf) {
         // locale (mSystemLocale), then reload the input locale list from the
         // latin ime settings (shared prefs) and reset the input locale
         // to the first one.
-        final String systemLocale = conf.locale.toString();
+        final Locale configLocale = conf.locale != null ? conf.locale
+                : (conf.getLocales().size() > 0 ? conf.getLocales().get(0) : Locale.getDefault());
+        final String systemLocale = configLocale.toString();
         if (!TextUtils.equals(systemLocale, mSystemLocale)) {
             mSystemLocale = systemLocale;
             if (mLanguageSwitcher != null) {
                 mLanguageSwitcher.loadLocales(
                         PreferenceManager.getDefaultSharedPreferences(this));
-                mLanguageSwitcher.setSystemLocale(conf.locale);
+                mLanguageSwitcher.setSystemLocale(configLocale);
                 toggleLanguage(true, true);
             } else {
                 reloadKeyboards();

src/keepass2android-app/app/App.cs

@@ -360,7 +360,17 @@ public void UpdateOngoingNotification()
       var ctx = LocaleManager.LocalizedAppContext;
       if (DatabaseIsUnlocked || QuickLocked)
       {
-        ContextCompat.StartForegroundService(ctx, new Intent(ctx, typeof(OngoingNotificationsService)));
+        try
+        {
+          ContextCompat.StartForegroundService(ctx, new Intent(ctx, typeof(OngoingNotificationsService)));
+        }
+        catch (Exception e)
+        {
+          // ForegroundServiceStartNotAllowedException (Android 12+): startForegroundService() is
+          // not allowed when called from a background-restricted context such as onTaskRemoved().
+          // In this case the notification simply cannot be updated; this is acceptable.
+          Kp2aLog.LogUnexpectedError(e);
+        }
       }
       else
       {
@@ -1023,7 +1033,10 @@ public void TriggerReload(Context ctx, Action<bool> actionOnResult)
       Handler handler = new Handler(Looper.MainLooper);
       handler.Post(() =>
           {
-            AskForReload((Activity)ctx, actionOnResult);
+            var activity = (ctx as Activity) ?? (ActiveContext as Activity);
+            if (activity == null)
+              return;
+            AskForReload(activity, actionOnResult);
           });
     }
 

src/keepass2android-app/services/BackgroundSyncService.cs

@@ -51,7 +51,7 @@ public override void OnCreate()
 
     public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId)
     {
-      if (intent.Action == ActionStop)
+      if (intent?.Action == ActionStop)
       {
         Log.Debug(Tag, "OnStartCommand: STOP");
         StopForeground(StopForegroundFlags.Remove);

src/keepass2android-app/views/GroupListItemView.cs

@@ -77,7 +77,9 @@ public override bool Activated
 
     public void SetRightArrowVisibility(bool visible)
     {
-      FindViewById(Resource.Id.right_arrow).Visibility = visible ? ViewStates.Visible : ViewStates.Invisible;
+      var arrow = FindViewById(Resource.Id.right_arrow);
+      if (arrow != null)
+        arrow.Visibility = visible ? ViewStates.Visible : ViewStates.Invisible;
     }
 
     public abstract void OnClick();

src/keepass2android-app/views/PwEntryView.cs

@@ -80,9 +80,9 @@ private PwEntryView(GroupBaseActivity groupActivity, PwEntry pw, int pos) : base
       _textView = (TextView)ev.FindViewById(Resource.Id.entry_text);
       _textView.TextSize = PrefsUtil.GetListTextSize(groupActivity);
 
-      Database db = App.Kp2a.FindDatabaseForElement(pw);
+      Database db = App.Kp2a.TryFindDatabaseForElement(pw);
 
-      ev.FindViewById(Resource.Id.entry_icon_bkg).Visibility = db.DrawableFactory.IsWhiteIconSet ? ViewStates.Visible : ViewStates.Gone;
+      ev.FindViewById(Resource.Id.entry_icon_bkg).Visibility = db?.DrawableFactory.IsWhiteIconSet == true ? ViewStates.Visible : ViewStates.Gone;
 
       _textviewDetails = (TextView)ev.FindViewById(Resource.Id.entry_text_detail);
       _textviewDetails.TextSize = PrefsUtil.GetListDetailTextSize(groupActivity);