Step to reproduce:
1. Open java file in editor.
2. Press Tools->Auto Comment... popup menu item.
3. Select some function and "New.." button to create tag. 
Select @since tag and press ok.
4. Put cursor to description box and press "Delete" button 
to delete tag.
5. Note that after deletion of tag buttons with html tags 
is still active. Press "<B>" button

REsult: Exception occured:

java.lang.ArrayIndexOutOfBoundsException: -1
	at java.util.Vector.elementAt(Vector.java:434)
	at javax.swing.DefaultListModel.get
(DefaultListModel.java:428)
	at 
org.netbeans.modules.javadoc.comments.JavaDocEditorPanel.fo
rmatButtonActionPerformed(JavaDocEditorPanel.java:651)
	at 
org.netbeans.modules.javadoc.comments.JavaDocEditorPanel.ac
cess$800(JavaDocEditorPanel.java:44)
	at 
org.netbeans.modules.javadoc.comments.JavaDocEditorPanel$13
.actionPerformed(JavaDocEditorPanel.java:484)
	at javax.swing.AbstractButton.fireActionPerformed
(AbstractButton.java:1786)
	at 
javax.swing.AbstractButton$ForwardActionEvents.actionPerfor
med(AbstractButton.java:1839)
	at 
javax.swing.DefaultButtonModel.fireActionPerformed
(DefaultButtonModel.java:420)
	at javax.swing.DefaultButtonModel.setPressed
(DefaultButtonModel.java:258)
	at 
javax.swing.plaf.basic.BasicButtonListener.mouseReleased
(BasicButtonListener.java:245)
	at java.awt.AWTEventMulticaster.mouseReleased
(AWTEventMulticaster.java:231)
	at java.awt.Component.processMouseEvent
(Component.java:5099)
	at java.awt.Component.processEvent
(Component.java:4896)
	at java.awt.Container.processEvent
(Container.java:1569)
	at java.awt.Component.dispatchEventImpl
(Component.java:3614)
	at java.awt.Container.dispatchEventImpl
(Container.java:1627)
	at java.awt.Component.dispatchEvent
(Component.java:3476)
	at 
java.awt.LightweightDispatcher.retargetMouseEvent
(Container.java:3483)
	at java.awt.LightweightDispatcher.processMouseEvent
(Container.java:3198)
	at java.awt.LightweightDispatcher.dispatchEvent
(Container.java:3128)
	at java.awt.Container.dispatchEventImpl
(Container.java:1613)
	at java.awt.Window.dispatchEventImpl
(Window.java:1606)
	at java.awt.Component.dispatchEvent
(Component.java:3476)
[catch] at java.awt.EventQueue.dispatchEvent
(EventQueue.java:456)
	at 
java.awt.EventDispatchThread.pumpOneEventForHierarchy
(EventDispatchThread.java:201)
	at 
java.awt.EventDispatchThread.pumpEventsForHierarchy
(EventDispatchThread.java:151)
	at java.awt.EventDispatchThread.pumpEvents
(EventDispatchThread.java:145)
	at java.awt.EventDispatchThread.pumpEvents
(EventDispatchThread.java:137)
	at java.awt.EventDispatchThread.run
(EventDispatchThread.java:100)

Reproduced with dev build.