Bug 193886 NPE is thrown when preview external CSS style in ppt[1205]
engine/org.eclipse.birt.report.engine.emitter.ppt/src/org/eclipse/birt/report/engine/emitter/ppt/PPTRender.java
for ( Iterator ite = filenames.iterator( ); ite.hasNext( ); )
						{
							pptOutput.write( ( "<o:File href=3D\""
									+ (String) ite.next( ) + "\"/>\n" ).getBytes( ) );
						}
					}
				}
				pptOutput.write( "</xml>\n".getBytes( ) ); 
				pptOutput.write( "\n".getBytes( ) ); 
				pptOutput.write( "--___Actuate_Content_Boundary___--\n".getBytes( ) ); 
			}
			catch ( IOException e )
			{
				e.printStackTrace( );
			}
		}
		pptOutput = null;
	}
	protected void endPage( ) throws IOException
	{
		String imageURI;
		
		for ( Iterator ite = currentImageContents.iterator( ); ite.hasNext( ); )
		{
			Object content = ite.next( );
			if ( content instanceof IImageContent )
			{
				IImageContent imageContent = (IImageContent) content;
				generateImageBytes( imageContent );
			}