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
{
				throw e;
			}
			byte[] data = null;
			if ( file != null )
			{
				try
				{
					data = new byte[file.available( )];
					file.read( data );
				}
				catch ( IOException e1 )
				{
					throw e1;
				}
			}
			pptOutput.write( base.encode( data ) );
		}
	}
	private void generateImageBytes( IImageContent imageContent )
			throws IOException
	{
		if ( imageContent.getURI( ) == null )
		{
			exportImageHeader( imageContent.getName( ) );
		}
		else
		{
			exportImageHeader( imageContent.getURI( ) );
		}