Displaying empty body for imported not-empty wiki topics

## Describe the bug
Importing topics to the wiki module, successfully replaced current topics with the new ones and it shows the list of all topics when clicking on the link (Show All Pages); but clicking on any imported topic, the module doesn't display its content. It needs one time opening of each topic and do updating it without the need to modify it.

## To Reproduce
Steps to reproduce the behavior:
1. Go to 'wiki module menu'
2. Click on 'Import'
3. Follow the procedure of importing new Wiki topics
4. See error: No content for the home page, also click on (Show All Pages) to display all topics, then click on some topics

## Expected behavior
Showing content of new topics.

## Screenshots
If applicable, add screenshots to help explain your problem.

## Error log
**Note: Debug DLL's**
There is no error message!

## Additional context
Opening a topic in Edit-mode, clicking on Update (no modifications needed) will fix the problem. It seems the problem relates to Cache field which is NULL after importing the topics.