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/executor/ExecutionContext.java
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)
	 */
	public Object evaluateCondExpr( IConditionalExpression expr )
	{
		int operator = expr.getOperator( );
		IScriptExpression testExpr = expr.getExpression( );
		IScriptExpression v1 = expr.getOperand1( );
		IScriptExpression v2 = expr.getOperand2( );
		if ( testExpr == null )
			return Boolean.FALSE;
		Object testExprValue = evaluate( testExpr.getText( ) );
		if ( IConditionalExpression.OP_NONE == operator )
		{
			return testExprValue;
		}
		Object vv1 = null;
		Object vv2 = null;
		if ( v1 != null )