/jp/ - Otaku Culture

Struggling to understand what ここじゃなんだ means in ここじゃなんだし近くの公園行きましょうか.
One thought I have is that なんだ is 何だ and it's like she's saying "doing it here is nothing" -> "It's not special to take your picture here (so lets go to the park)".
Another is that it's a contraction of ここではなのだ, but I don't feel confident about what this could mean here. Maybe like "If we are definitely doing it here lets go to the park".