Hmmm, ok... I guess it has something to do with the deprecated Application class, which has been replaced by the Component.js
Probably the sap.ui.app library now does not exist anymore... But as a test, could you then try and *add* the sap.ui.app library to the bootstrapper? Maybe it works...
However, a better solution would be if you could refactor your application so it uses the Component.js class instead of the Application.js. See also the best-practices guide at SAPUI5 SDK - Demo Kit