ClassFiles(java.io.File) crashes when the given file doesn't exist

[Daniel Klauer]

https://bitbucket.org/delors/bat/src/6def8db391352029e15f45eea513ae0041aab255/core/src/main/scala/de/tud/cs/st/bat/reader/ClassFileReader.scala?at=master#cl-471

If file.isFile() is false, the directory code path will be taken, but without any further checks. Then file.listFiles() is called but may return null (in case the File object doesn't represent an existing directory either), which causes the crash in the following .par.

[Michael Eichberg]

fixed issue #23

→ <<cset f771d838ca49>>