Exception Adding/Editing Property Definition's Value Constraint In CND Editor

In CND Editor, if you select a property in the Properties Section table, and double-click the table row or click the editor toolbar button, the Property Definition Editor dialog opens. In the property dialog, if you Add or Edit a value constraint, a Value Editor dialog is displayed. If the user types in the textfield an error occurs and the OK button can never be enabled. Here is the error from the log:

java.lang.UnsupportedOperationException
at java.util.AbstractList.add(AbstractList.java:131)
at java.util.AbstractList.add(AbstractList.java:91)
at org.jboss.tools.modeshape.jcr.ui.cnd.PropertyDialog$31$1.validate(PropertyDialog.java:1193)
at org.jboss.tools.modeshape.jcr.ui.cnd.StringValueEditorDialog.updateState(StringValueEditorDialog.java:185)
at org.jboss.tools.modeshape.jcr.ui.cnd.StringValueEditorDialog.handleValueChanged(StringValueEditorDialog.java:172)
at org.jboss.tools.modeshape.jcr.ui.cnd.StringValueEditorDialog$1.modifyText(StringValueEditorDialog.java:149)