fix(app): buildClasspath: check if folder exists before walk-through

src/main/java/de/hftstuttgart/modocot/Testrunner.java

@@ -111,6 +111,11 @@ public class Testrunner
             {
                 path = path.substring(0, path.length() - 1);
                 File pathFile = new File(path);
+                if (!pathFile.exists() || !pathFile.isDirectory())
+                {
+                    continue;
+                }
+
                 for (File file : Objects.requireNonNull(pathFile.listFiles()))
                 {
                     if (file.isFile() && file.getName().endsWith(".jar"))