bugfix: markdown would fail if plantuml jar is not configured

core/src/main/java/de/srsoftware/umbrella/core/Util.java

@@ -72,7 +72,7 @@ public class Util {
 	public static String markdown(String source){
 		if (source == null) return source;
 		try {
-			if (plantumlJar.exists()) {
+			if (plantumlJar != null && plantumlJar.exists()) {
 				var matcher = UML_PATTERN.matcher(source);
 				if (matcher.find()) {
 					var uml = matcher.group(0).trim();