Use java 17

pom.xml

@@ -16,7 +16,7 @@
 	<description>PlayWall Server</description>
 
 	<properties>
-		<java.version>21</java.version>
+		<java.version>17</java.version>
 
 		<snakeyaml.version>2.2</snakeyaml.version>
 	</properties>

src/main/java/de/tobias/playwall/service/ArtifactoryClient.java

@@ -53,7 +53,10 @@ public class ArtifactoryClient
 				.map(child -> versionTokenizer.getVersion(child.getUri()))
 				.sorted(Comparator.comparing(Version::major).thenComparing(Version::minor).thenComparing(Version::patch))
 				.toList();
-		return version.getLast();
+		if (version.isEmpty()) {
+			return null;
+		}
+		return version.get(version.size() - 1);
 	}
 
 	private record ArchiveViewSourceRequest(String archivePath, String repoKey, String sourcePath)