code: protected final IData checkItemIfDeleted(final IData pToCheck) {
          if (pToCheck == null) {
              throw new IllegalStateException(new StringBuilder("Data not existing.").toString());
          } else if (pToCheck instanceof DeletedData) {
              return null;
          } else {
              return pToCheck;
          }
      }
docs: Method to check if an {@link IData} is a deleted one.
  
  @param pToCheck
  of the IItem
  @return the item if it is valid, null otherwise