code: public static void checkId(CmsUUID id, boolean canBeNull) {
  
          if (canBeNull && (id == null)) {
              return;
          }
          if ((!canBeNull && (id == null)) || id.isNullUUID()) {
              throw new IllegalArgumentException(Messages.get().key(Messages.ERR_INVALID_UUID_1, id));
          }
      }
docs: Check that the given id is not the null id.<p>
  
  @param id the id to check
  @param canBeNull only if flag is set, <code>null</code> is accepted
  
  @see #isNullUUID()