Fix error on cli if webroot directory doesnt exist

Author: TBlueF

common/src/main/java/de/bluecolored/bluemap/common/WebFilesManager.java

@@ -112,6 +112,7 @@ public void updateFiles() throws IOException {
         if (zippedWebapp == null) throw new IOException("Failed to open bundled webapp.");
 
         // extract zip to webroot
+        Files.createDirectories(webRoot);
         FileHelper.extractZipFile(zippedWebapp, webRoot, StandardCopyOption.REPLACE_EXISTING);
 
         // set version in index.html