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
if ( pptOutput == null )
		{
			Object value = services.getOption( RenderOption.OUTPUT_STREAM );
			if ( value instanceof OutputStream )
			{
				pptOutput = (OutputStream) value;
			}
			
			
			else
			{
				try
				{
					file = new File( REPORT_FILE );
					pptOutput = new FileOutputStream( file );
				}
				catch ( FileNotFoundException e )
				{
					logger.log( Level.SEVERE, e.getMessage( ), e );
				}
			}
		}
	}
	/**
	 * Creates a PPT Document.
	 * 
	 * @param rc