Array functions, array_length behavior given an empty array

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/13/functions-array.html
Description:

For whom it may concern,

I'd like to propose an extension for `array_length` function description.

Currently, it does not cover the case of an empty array:

https://www.postgresql.org/docs/13/functions-array.html
Table 9.52. Array Functions. Row 5

The description reads as `Returns the length of the requested array
dimension.`

For me, an expected result for an empty array would be `0`, but it is
`NULL`.
Tested on `PostgreSQL 13.4` with query `SELECT
ARRAY_LENGTH(ARRAY[]::CHARACTER VARYING[],1);`

I believe, such case deserves to be mentioned in the description and/or in
examples.

With best regards,
Oleg Rekin