mi dā lo stesso problema

lancio il file cosi

java -jar M.jar

e mi dā questo errore

Uncaught error fetching image:
java.lang.NullPointerException
at sun.awt.image.URLImageSource.getConnection(URLImag eSource.java:99)
at sun.awt.image.URLImageSource.getDecoder(URLImageSo urce.java:108)
at sun.awt.image.InputStreamImageSource.doFetch(Input StreamImageSource.j
ava:251)
at sun.awt.image.ImageFetcher.fetchloop(ImageFetcher. java:168)
at sun.awt.image.ImageFetcher.run(ImageFetcher.java:1 36)

help