Bug 57707: Hotfix, don't push undefined onto wikitext array

This might have been broken in 283bfd55, but this patch just works around the
breakage for now by not pushing undefined onto the wikitext array. Proper
investigation and fix to be done.

Change-Id: Ic1706c8da69c0046b1acd39f1e8b3de55a3fee92
Merge "Bug 57707: Hotfix, don't push undefined onto wikitext array"