Bug 163018 An error extension will lead the report contain chart can't be opened and can not new a report.
Details: An error extension will lead the report contain chart can't open In org.eclipse.birt.report.tests.model has an error extension. When run the birt use workbenck, the report contain chart can't be opened and it can not new a report.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/metadata/ElementDefn.java
* User-element inheritance uses JavaScript-like prototype inheritance.
 * <p>
 * BIRT does define and "extended element" that the user can define from
 * scratch, but even this follows the same rules. An extended element is not a
 * new type, it is just a particular set of customizations of the predefined
 * "extended" type.
 * <p>
 * User-defined inheritance is limited to elements of the same type. A label can
 * extend another label, but it cannot extend a data element, say.
 * <p>
 * System inheritance is used to define properties in a base class that should
 * be inherited by derived classes. User-inheritance implicitly inherits
 * properties, but focuses on inheriting property values. That is, user
 * inheritance allows Label B to inherit a font color of red from Label A. As
 * noted above, elements can define user properties. These property definitions
 * also are inherited with user inheritance. that is, if Label A defines a new
 * "Blink Rate" property, then label B (which extends label A) also has this
 * property.
 * 
 * <h3>Styles</h3>
 * 
 * BIRT includes the idea of styles. A style is simply a set of visual
 * information defined once in a design but used by many elements. At the core
 * level that we are discussing here, styles introduce a couple of interesting
 * twists to the design of the meta-data and element systems.
 * <p>
 * First some element types are defined to "have" a style. Having a style means
 * two things. First, the user can specify the name of a shared style to
 * associate with the element. Second, means that the element logically has a
 * "private style" that includes all the style properties relevant to that