jpackage --app-image /tmp does not provide a helpful message with a malformed app-image.

Example 1:
 jpackage --app-image /tmp --package-type deb --output x

Output:
Bundler DEB Installer skipped because of a configuration problem: java.lang.NullPointerException.

Example 2:
jpackage --app-image /tmp

Output:
Error: Option [--app-image] is not valid with package-type [null].

Example 3:
mkdir /tmp/x
touch /tmp/x/y
jpackage --app-image /tmp/x --package-type deb --output x --name xxxx

Output 3:
java.nio.file.NoSuchFileException: /tmp/jdk.jpackage13842042862336393495/images/linux-deb.image/xxxx-1.0/opt/xxxx/bin/xxxx.png

Example 4: (Even with a well formed app image) if the --name is missing the message is poor.
jpackage -o out --app-image out/skara --package-type deb

Output 4:
Bundler DEB Installer skipped because of a configuration problem: java.lang.NullPointerException.