This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
To avoid an exception to be thrown, put in the tiles:insert tag that can be optional the attribute ignore="true"
ignore: If this attribute is set to true, and the attribute specified by the name does not exist, simply return without writing anything. The default value is false, which will cause a runtime exception to be thrown. [RT Expr]