It's a matter of the flow of the speech and continuity. If there is something after (hunák) then the last vowel is added (there are some rules of speech in Arabic concerning vowel-less consonants and consonant clusters ...etc).
If continuity after (hunák) is not required (imagine pointing something to someone and simply saying there!), then the last vowel is not required because there is nothing coming after (hunák).
Same thing for sentences in general; the last word in the sentence can drop its last vowel because the sentence is finished and nothing is coming after it.