Creation of Web Installers throws an exception

The creation of a Web Installers based on the sample installation throws the following exception:

-> Fatal error :
null/packsinfo.xml (No such file or directory)
java.io.FileNotFoundException: null/packsinfo.xml (No such file or directory)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(FileOutputStream.java:179)
at java.io.FileOutputStream.<init>(FileOutputStream.java:70)
at java.io.FileWriter.<init>(FileWriter.java:46)
at com.izforge.izpack.compiler.Packager.writePacks(Unknown Source)
at com.izforge.izpack.compiler.PackagerBase.writeInstaller(Unknown Source)
at com.izforge.izpack.compiler.Packager.createInstaller(Unknown Source)
at com.izforge.izpack.compiler.Compiler.createInstaller(Unknown Source)
at com.izforge.izpack.compiler.CompilerConfig.executeCompiler(Unknown Source)
at com.izforge.izpack.compiler.CompilerConfig.main(Unknown Source)
at com.izforge.izpack.compiler.Compiler.main(Unknown Source)

An immediate workaround is to create a 'null' directory.