What does UndeclaredThrowableException mean when I delete a schema file?

This FAQ only applies to NetBeans 5.5 Beta

Sometimes when I create a Java Application, open a new or sample schema, Select Projects and right-click the schema file, and then select Delete, the schema is deleted, but the following NPE is thrown.

java.lang.reflect.UndeclaredThrowableException
    at $Proxy9.resultChanged(Unknown Source)

Answer: Avoid deleting the schema for this release.

Reference Issue 82519

Applies to: NetBeans 5.5

Platforms: all