Error out of the box with ConstraintLayout

[Jorge]

As stated in #32, im facing this same error ("Couldn't resolve @id/default_state") inmediately after adding to my layout -ConstraintLayout- the sample xml code :

    <io.github.yavski.fabspeeddial.FabSpeedDial
        android:id="@+id/pressed_state"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|start"
        app:fabGravity="bottom_start"
        app:fabMenu="@menu/menu_main"
        app:miniFabBackgroundTint="@android:color/white"
        app:miniFabDrawableTint="?attr/colorPrimaryDark"
        app:miniFabTitleTextColor="?attr/colorPrimaryDark" />

Obviusly I have no element with such id... I've seen when creating a new element and giving it the issued @id, it looks forward for @id/pressed_state, but not sure about how to fix this up.