Bug 123523 Previewing a scripted data set mapped to a java event handler throws NPE
When previewing a scripted data set we try to get a class loader from the ExecutionContext. (See ScriptExecutor.getClassUsingCustomClassPath). The context will be null in this case. The reason for using the context is to use cached class loaders when possible. Need to use some other mechanism to get the class loader if the context is null. We can either provide an external map to use as cache, or not bother with caching at all.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/script/element/IReportItem.java
* @param dimension
	 *            dimension string with optional unit suffix.
	 * @throws ScriptException
	 *             if the string is not valid
	 */
	void setHeight( String dimension ) throws ScriptException;
	/**
	 * Sets the item's height to a value in default units. The default unit may
	 * be defined by the property in BIRT or the application unit defined in the
	 * design session.
	 * 
	 * @param dimension
	 *            the new value in application units.
	 * @throws ScriptException
	 *             if the property is locked.
	 */
	void setHeight( double dimension ) throws ScriptException;
	/**
	 * Sets the item's width using a dimension string with optional unit suffix
	 * such as "10" or "10pt". If no suffix is provided, then the units are
	 * assumed to be in the design's default units. Call this method to set a
	 * string typed in by the user.
	 * 
	 * @param dimension
	 *            dimension string with optional unit suffix.
	 * @throws ScriptException
	 *             if the string is not valid
	 */
	void setWidth( String dimension ) throws ScriptException;
	/**