FIX. RadRibbonForm - theme is not applying correctly, when some changes are made to ribbon button while RadRibbonBar is collapsed.

Steps to reproduce:
1. Add button to some ribbon group.
2. Collapse the ribbon.
3. Disable this button.
4. Enable this button.
5. Expand the ribbon.

Workaround - subscribe to ExpandedStateChanged  event and reapply the theme. For example:

            this.radRibbonBar1.ExpandedStateChanged += new EventHandler(radRibbonBar1_ExpandedStateChanged);


        void radRibbonBar1_ExpandedStateChanged(object sender, EventArgs e)
        {
            this.radRibbonBar1.ElementTree.ApplyThemeToElementTree();
        }