MaterialListBox#getIndex(String value) throws IndexOutOfBoundsException

[rodrigoborgesdeoliveira]

If the MaterialListBox has an empty placeholder, the following code

public int getIndex(T value) {
        int count = getItemCount();
        for (int i = 0; i < count; i++) {
            if (Objects.equals(getValue(i), value)) {
                return i;
            }
        }
        return -1;
    }

throws an IndexOutOfBoundsException at getValue(i).
The reason is that the getItemCount() will also count the empty placeholder as an item, so when calling getValue(i) in the for loop, it will then call getValueInternal(index + getIndexOffset()), which will, in the last element, try to get a position = count.
Example:
If the list has no items, count will be 1 and getValue(0) will translate to getValueInternal(1). Since there is only one element (index 0), it will throw the exception.

[kevzlou7979]

Merged via 6804e9f. Again thanks for your contribution.