Follow-up 94c3984: not all ResultTypes request text.word_count

Specifically, TitleResults and InterwikiResults don't. So the best
thing there is just to pretend we have no words. Usually we're in a
code path that won't care; worst case scenario we lie a little bit.

Change-Id: I7d04626a5485f750622921de7a78cad4f8322fb7