Duplicate note, in Arrays section "Attempting to access an array key which has not been defined ...

[Marqitos]

Duplicate note, with faulty indentation, in the same section, which is why it appears twice on the same page of the documentation.

Attempting to access an array key which has not been defined is the same as accessing any other undefined variable ...

It appears in file language/types/array.xml, on the lines 434 and 714.

If it is intentional, you would only have to correct the indentation, and if so in the second note, indicate "We reiterate ..., or similar.