Can't add icon to the main fab icon button

[MostafaKhaled2017]

I have a fab icon menu that contains 2 fab icons I have added icons for the 2 fab icons but I can't add an icon for the main item which opens the 2 other items.

this is my xml code :
` <com.getbase.floatingactionbutton.FloatingActionsMenu
android:id="@+id/multiple_actions"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
fab:fab_addButtonColorNormal="@color/colorPrimary"
fab:fab_addButtonColorPressed="@color/colorPrimary"
fab:fab_addButtonPlusIconColor="@color/colorPrimary"
fab:fab_labelStyle="@style/menu_labels_style"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintBottom_toTopOf="@id/navigation"
app:srcCompat="@drawable/add"
app:layout_insetEdge="bottom" >

    <com.getbase.floatingactionbutton.FloatingActionButton
        android:id="@+id/fabChallenge"
        app:fab_icon="@drawable/elect"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        fab:fab_colorNormal="@color/white"
        fab:fab_title="بدء تحدى جديد"
        fab:fab_colorPressed="@color/colorPrimary"/>

    <com.getbase.floatingactionbutton.FloatingActionButton
        android:id="@+id/fabAddPost"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        fab:fab_colorNormal="@color/white"
        app:fab_icon="@drawable/add"
        fab:fab_title="إضافة منشور"
        fab:fab_colorPressed="@color/colorPrimary"/>

</com.getbase.floatingactionbutton.FloatingActionsMenu>`