Sorry, I messed up quickly — it says Template Options, not Menu.
#__template_styles.params
Style #9
This is where it is, and somewhere in the Yootheme config there’s embedded JavaScript.
I’m currently tracking down the culprit (most likely FP), and the fix (including a clearer message showing exactly where the code comes from, with highlighting of the exact spot instead of the cut-off start of the params) will be included in 2.6.2.
If you find it in that table, feel free to post the full field here anyway.