Empty table cells are not rendered nicely

Consider a table like below:

**(browse/search/modify**)))|**Requests per second**|**Concurrency**|**Max user capacity**|**Average user response time**
|Heavy read|80 / 10 / 10||||

Such a table is not rendered nicely on browsers (the empty cells are not rendered).

As a quick workaround, a space can be added as the content of the table cell. Following table renders nicely:

**(browse/search/modify**)))|**Requests per second**|**Concurrency**|**Max user capacity**|**Average user response time**
|Heavy read|80 / 10 / 10| | | | 

But this "adding space to empty cells" should be done in xhtml renderer automatically so that users won't have to do it manually.