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/EncryptionHelperExtensionLoader.java
private static final String EXTENSION_NAME_ATTRIB = "extensionName"; 
		private static final String CLASS_ATTRIB = "class"; 
		/**
		 * Loads the extension.
		 * 
		 * @param elementTag
		 *            the element tag
		 * @throws ExtensionException
		 *             if the class some attribute specifies can not be
		 *             instanced.
		 */
		public void loadElement( IConfigurationElement elementTag )
				throws ExtensionException
		{
			String extensionName = elementTag
					.getAttribute( EXTENSION_NAME_ATTRIB );
			String className = elementTag.getAttribute( CLASS_ATTRIB );
			checkRequiredAttribute( EXTENSION_NAME_ATTRIB, extensionName );
			checkRequiredAttribute( CLASS_ATTRIB, className );
			try
			{
				IEncryptionHelper helper = (IEncryptionHelper) elementTag
						.createExecutableExtension( CLASS_ATTRIB );
				IEncryptionHelper registeredHelper = MetaDataDictionary
						.getInstance( ).getEncryptionHelper( );
				if ( registeredHelper != SimpleEncryptionHelper.getInstance( ) )
				{
					throw new ExtensionException(
							new String[]{className},
							ExtensionException.DESIGN_EXCEPTION_ENCYRPTION_EXTENSION_EXISTS );