Fix IndexOutOfBoundsException in HabitCardListAdapter

app/src/main/java/org/isoron/uhabits/activities/habits/list/model/HabitCardListAdapter.java

@@ -105,11 +105,10 @@ public class HabitCardListAdapter
      * Returns the item that occupies a certain position on the list
      *
      * @param position position of the item
-     * @return the item at given position
+     * @return the item at given position or null if position is invalid
-     * @throws IndexOutOfBoundsException if position is not valid
      */
     @Deprecated
-    @NonNull
+    @Nullable
     public Habit getItem(int position)
     {
         return cache.getHabitByPosition(position);
@@ -314,6 +313,8 @@ public class HabitCardListAdapter
     public void toggleSelection(int position)
     {
         Habit h = getItem(position);
+        if (h == null) return;
+
         int k = selected.indexOf(h);
         if (k < 0) selected.add(h);
         else selected.remove(h);

app/src/main/java/org/isoron/uhabits/activities/habits/list/model/HabitCardListCache.java

@@ -93,12 +93,12 @@ public class HabitCardListCache implements CommandRunner.Listener
      * Returns the habits that occupies a certain position on the list.
      *
      * @param position the position of the habit
-     * @return the habit at given position
+     * @return the habit at given position or null if position is invalid
-     * @throws IndexOutOfBoundsException if position is not valid
      */
-    @NonNull
+    @Nullable
-    public Habit getHabitByPosition(int position)
+    public synchronized Habit getHabitByPosition(int position)
     {
+        if(position < 0 || position >= data.habits.size()) return null;
         return data.habits.get(position);
     }