[MARTIFACT-13] take care about missing zip entry
diff --git a/src/main/java/org/apache/maven/plugins/artifact/buildinfo/ReferenceBuildinfoUtil.java b/src/main/java/org/apache/maven/plugins/artifact/buildinfo/ReferenceBuildinfoUtil.java
index f5865b9..5bcecb8 100644
--- a/src/main/java/org/apache/maven/plugins/artifact/buildinfo/ReferenceBuildinfoUtil.java
+++ b/src/main/java/org/apache/maven/plugins/artifact/buildinfo/ReferenceBuildinfoUtil.java
@@ -52,6 +52,7 @@
 import java.util.jar.Attributes;
 import java.util.jar.JarFile;
 import java.util.jar.Manifest;
+import java.util.zip.ZipEntry;
 
 /**
  * Utility to download or generate reference buildinfo.
@@ -234,7 +235,12 @@
     private String extractOsName( Artifact a, JarFile jar )
     {
         String entryName = "META-INF/maven/" + a.getGroupId() + '/' + a.getArtifactId() + "/pom.properties";
-        try ( InputStream in = jar.getInputStream( jar.getEntry( entryName ) ) )
+        ZipEntry zipEntry = jar.getEntry( entryName );
+        if ( zipEntry == null )
+        {
+            return null;
+        }
+        try ( InputStream in = jar.getInputStream( zipEntry ) )
         {
             String content = IOUtil.toString( in, StandardCharsets.UTF_8.name() );
             log.debug( "Manifest content: " + content );