linkeddata: Fix broken check in PageDataRequestHandler

linkeddata: Fix broken check in PageDataRequestHandler

First I noticed a weird check that assumes that explode() would return
an integer. But it returns an array of strings. There is obviously a
count() missing.

Then I started simplifying the code:
* The count can only be 2 or 1, never anything else.
* If it is one, the first element in the array contains the original string.
* The empty string is already checked above and can never end down there.
* Finally I made the remaining `if ( … ) return true else return false` a
  straight `return …`.

Change-Id: I289144e64f449ee0875009aaa22e10a5c0eb2734