Bug 159076 PDF emitter needs to response if "com.lowagie.itext" is missed.
Previously on GUI, preview in PDF has to check the "com.lowagie.itext" is included in BIRT firstly. Now we think GUI doesn't need to do any check for emitters and in order to avoid any hard coded behaviors about emitter contribution, this check is remove from GUI codes. So, PDF emitter should be responsible to response if required resources is missed.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/RenderTask.java
/*******************************************************************************
 * Copyright (c) 2004 Actuate Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *  Actuate Corporation  - initial API and implementation
 *******************************************************************************/
package org.eclipse.birt.report.engine.api.impl;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;