What does this message mean from my boss?

Me and my boss flirt a lot and generally just work really well as a team. Anyway, I sent a joke photo of myself outside our favourate lunch spot (I've never sent a photo of myself before) as i know he would be jelous I was there and he resonded " im not going to relpy as i can't say anything nice"

Are you reading thats as he wants to say i look good in the photo or is he joking that he's not happy im there without him?

I just got a different vibe from the message! And Yes i already know we shouldn't be too friendly but that ship has sailed!

Thanks

Updates
+1 y
Just an FYI that we both followed up with a little joke and nothing weird followed but this message stumped me a but
What does this message mean from my boss?
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