(Bug 67857): Dont push empty "" in table-fixup code.

* The following wikitext now parses properly without a ""
  content in the parts array.

{|
| {{Tabelcel tennis/vereenvoudigd|X}}
|}

Change-Id: Iff1193c40694fbbebd77611575d4e640b1bb3117
Merge "(Bug 67857): Dont push empty "" in table-fixup code."