Bug 213680 [2.2.2]Chart script can not be cleaned completely.
Description: Reset script or delete all script does not work. build version: v20071221-0630 steps to reproduce: 1. New a report. 2. New a chart. 3. Enter some script for the chart and save the report. 4. Click the reset scirpt button or delete all script. 5. Save the report and switch to layout,then switch back to script page. Expected result: Script are cleaned. Actual result: Script are not cleaned. Note: If you delete part of the script, it works.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/metadata/ElementPropertyDefn.java
* 
	 * @return <code>true</code>.
	 */
	public boolean isVisible( )
	{
		return true;
	}
	/**
	 * Checks whether the property value is read-only in the property sheet.
	 * 
	 * @return <code>false</code>.
	 */
	public boolean isReadOnly( )
	{
		return false;
	}
	/**
	 * Checks whether the property value can be edited by the user in the
	 * property sheet.
	 * 
	 * @return <code>true</code> if the property value is read-only,
	 *         <code>false</code> otherwise.
	 */
	public boolean isEditable( )
	{
		return !( getTypeCode( ) == IPropertyType.CHOICE_TYPE );
	}
	/**
	 * Returns the method information of this property.
	 *