Cannot read metadata from jar that is exactly 1 directory from path root

[IzzelAliz]

Launch with argument like -DlegacyClassPath=/path/to.jar would throw NPE and fail because artifactMaybe would be / so that artifactMaybe.getFileName() return null.

java.lang.NullPointerException: Cannot invoke "java.nio.file.Path.toString()" because the return value of "java.nio.file.Path.getFileName()" is null
	at cpw.mods.securejarhandler@0.9.54/cpw.mods.jarhandling.JarMetadata.fromFileName(JarMetadata.java:60)
	at cpw.mods.securejarhandler@0.9.54/cpw.mods.jarhandling.JarMetadata.from(JarMetadata.java:44)
	at cpw.mods.securejarhandler@0.9.54/cpw.mods.jarhandling.SecureJar.lambda$from$1(SecureJar.java:42)
	at cpw.mods.securejarhandler@0.9.54/cpw.mods.jarhandling.SecureJar$$Lambda$97/0x00000000f4842b00.apply(Unknown Source)
	at cpw.mods.securejarhandler@0.9.54/cpw.mods.jarhandling.impl.Jar.<init>(Jar.java:133)
	at cpw.mods.securejarhandler@0.9.54/cpw.mods.jarhandling.SecureJar.from(SecureJar.java:58)
	at cpw.mods.securejarhandler@0.9.54/cpw.mods.jarhandling.SecureJar.from(SecureJar.java:50)
	at cpw.mods.securejarhandler@0.9.54/cpw.mods.jarhandling.SecureJar.from(SecureJar.java:42)
	at cpw.mods.bootstraplauncher@0.1.17/cpw.mods.bootstraplauncher.BootstrapLauncher.main(BootstrapLauncher.java:60)

securejarhandler/src/main/java/cpw/mods/jarhandling/JarMetadata.java

Lines 53 to 62 in 026bc1f

	static SimpleJarMetadata fromFileName(final Path path, final Set<String> pkgs, final List<SecureJar.Provider> providers) {
	// detect Maven-like paths
	Path versionMaybe = path.getParent();
	if (versionMaybe != null)
	{
	Path artifactMaybe = versionMaybe.getParent();
	if (artifactMaybe != null && path.getFileName().toString().startsWith(artifactMaybe.getFileName().toString() + "-" + versionMaybe.getFileName().toString()))
	{
	var name = artifactMaybe.getFileName().toString();