#1435 Fix StringIndexOutOfBoundsException when title is blank

package it.niedermann.owncloud.notes.main.slots;

import android.content.Context;

import android.text.TextUtils;

import androidx.annotation.NonNull;

import androidx.annotation.Nullable;

import java.util.ArrayList;

import java.util.List;

import java.util.Optional;

import it.niedermann.owncloud.notes.R;

import it.niedermann.owncloud.notes.main.items.section.SectionItem;

        String lastInitials = null;

        for (int i = 0; i < noteList.size(); i++) {

            final var currentNote = noteList.get(i);

            String initials = currentNote.getTitle().substring(0, 1).toUpperCase();

            final var title = currentNote.getTitle();

            String initials = "";

            if(!TextUtils.isEmpty(title)) {

                initials = title.substring(0, 1).toUpperCase();

                if (!initials.matches("[A-Z\\u00C0-\\u00DF]")) {

                    initials = initials.matches("[\\u0250-\\uFFFF]") ? context.getString(R.string.simple_other) : "#";

                }

            }

            if (i > 0 && !initials.equals(lastInitials)) {

                itemList.add(new SectionItem(initials));

            }

package it.niedermann.owncloud.notes.main.slots;

import static org.junit.Assert.assertEquals;

import androidx.test.core.app.ApplicationProvider;

import org.junit.Test;

import org.junit.runner.RunWith;

import org.robolectric.RobolectricTestRunner;

import java.util.Calendar;

import java.util.List;

import it.niedermann.owncloud.notes.main.items.section.SectionItem;

import it.niedermann.owncloud.notes.persistence.entity.Note;

@RunWith(RobolectricTestRunner.class)

public class SlotterUtilTest {

    @Test

    public void fillListByInitials_shouldAddSectionItems() {

        final var notes = List.of(

                new Note(1L, Calendar.getInstance(), "Aaa", "", "", false, ""),

                new Note(1L, Calendar.getInstance(), "Abc", "", "", false, ""),

                new Note(1L, Calendar.getInstance(), "Bbb", "", "", false, ""),

                new Note(1L, Calendar.getInstance(), "Bcd", "", "", false, ""),

                new Note(1L, Calendar.getInstance(), "Def", "", "", false, "")

        );

        final var items = SlotterUtil.fillListByInitials(ApplicationProvider.getApplicationContext(), notes);

        assertEquals(2, items.stream().filter(item -> item instanceof SectionItem).count());

        assertEquals(SectionItem.class, items.get(2).getClass());

        assertEquals(SectionItem.class, items.get(5).getClass());

    }

    @Test

    public void fillListByInitials_shouldAcceptEmptyTitles() {

        final var notes = List.of(

                new Note(1L, Calendar.getInstance(), "", "", "", false, ""),

                new Note(2L, Calendar.getInstance(), "Foo", "", "", false, ""),

                new Note(3L, Calendar.getInstance(), "Bar", "", "", false, "")

        );

        final var items = SlotterUtil.fillListByInitials(ApplicationProvider.getApplicationContext(), notes);

    }

}