code: private static String getModuleFolder(String moduleName) {
  
          if (moduleName == null) {
              return null;
          }
          CmsModule module = OpenCms.getModuleManager().getModule(moduleName);
          if (module != null) {
              for (String resource : module.getResources()) {
                  if (CmsStringUtil.comparePaths("/system/modules/" + moduleName, resource)) {
                      return resource;
                  }
              }
          }
          return null;
      }
docs: Tries to find the module folder under /system/modules for a given module.<p>
  
  @param moduleName the name of the module
  
  @return the module folder, or null if this module doesn't have one