Bug 121111 Bad event handler class name does not cause an error
Open a report design, open any Data Set's Property editor. Type in an invalid Java class name for the "Event Handler Class" property, say "aaa". Preview a report that uses that Data Set. The report executes normally. No error is shown. Event handlers are an integral part of a report design, and if a script handler class is not found, or if the handler throws a runtime exception, Report Engine should either stop the report execution, or show the error message in the generated report. (Tested with the 2005-12-15 nightly build)
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/executor/ExecutionContext.java
*            an expression handle used to evaluate DtE expression
	 * @return the evaluated result of the expression
	 */
	public Object evaluate( IBaseExpression expr )
	{
		assert expr != null;
		try
		{
			return getDataEngine( ).evaluate( expr );
		}
		catch ( Throwable t )
		{
			
			log.log( Level.SEVERE, t.getMessage( ), t );
			addException( new EngineException(
					MessageConstants.INVALID_EXPRESSION_ERROR, expr, t ) ); 
		}
		return null;
	}
	/**
	 * evaluate conditional expression. A conditional expression can have an
	 * operator, one LHS expression, and up to two expressions on RHS, i.e.,
	 * 
	 * testExpr operator operand1 operand2 or testExpr between 1 20
	 * 
	 * Now only support comparison between the same data type
	 * 
	 * @param expr
	 *            the conditional expression to be evaluated
	 * @return a boolean value (as an Object)