XIVY-10310 provide feedback if URI setup failed

- e.g. due to missing ivyTestRuntime.proprties at designer or
engine-launch jvm param in Maven.

web-tester/src/main/java/com/axonivy/ivy/webtest/engine/BaseEngineUrl.java

@@ -32,14 +32,19 @@
  */
 class BaseEngineUrl {
 
+  private static final String DEFAULT_URL = "http://localhost:8081/";
   static final String TEST_ENGINE_URL = "test.engine.url";
 
   static String url() {
     return new BaseEngineUrl().evaluate();
   }
 
   private String evaluate() {
-    var engineUrl = System.getProperty(TEST_ENGINE_URL, "http://localhost:8081/");
+    var engineUrl = System.getProperty(TEST_ENGINE_URL);
+    if (engineUrl == null || engineUrl.isBlank()) {
+      System.err.println("Missing system property '"+TEST_ENGINE_URL+"' falling back to '"+DEFAULT_URL+"'.");
+      engineUrl = DEFAULT_URL;
+    }
     try {
       return evaluate(engineUrl);
     } catch(Exception ex) {