MySQL store procedure use select responce in INSERT...SELECT where in array
I'll choose to make the database generate a (virtual) table with all (id_v, lang) pairs that you are expected to have at the end.
To do so, you start by getting the list (actually set) of all DISTINCT lang:
SELECT DISTINCT
    lang
FROM
    ven_data ;

... and let's imagine it is this one

| lang |
| :--- |
| EN   |
| FR   |
| IT   |
| CA   |
| DE   |
| DK   |
| GR   |
| NL   |

We do the same to get the set of all DISTINCT id_v:
SELECT DISTINCT
    id_v
FROM
    ven_data ;


| id_v |
| ---: |
|    1 |
|    2 |
|    3 |
|    4 |
|    8 |
|    9 |
|   11 |
|   12 |
|   13 |

What should be in your ven_data table is actually the cartesian product of both sets. That is accomplished in SQL by means of a CROSS JOIN.
That results in:

id_v | lang
---: | :---
   1 | EN  
   2 | EN  
   3 | EN  
   4 | EN  
   8 | EN  
   9 | EN  
  11 | EN  
  12 | EN  
  13 | EN  
   [...]
   1 | NL  
   2 | NL  
   3 | NL  
   4 | NL  
   8 | NL  
   9 | NL  
  11 | NL  
  12 | NL  
  13 | NL  

What you actually want to do is INSERT in your table all the rows in this cartesian product that aren't already there.
You do this by means of:
INSERT INTO 
    ven_data
    (id_v, lang)
SELECT
    id_v, lang
FROM
    -- The whole set of (id_v, lang) pairs
    (SELECT DISTINCT
        lang
    FROM
        ven_data
    ) AS languages
    CROSS JOIN
    (SELECT DISTINCT
        id_v
    FROM
        ven_data
    ) AS id_list
WHERE
    -- The pair (id_v, lang) is not already in place
    NOT EXISTS
    (SELECT 
        1
    FROM 
        ven_data v2
    WHERE 
        v2.id_v = id_list.id_v AND v2.lang = languages.lang
    ) ;

Note that this WHERE condition can also be written in more than one fashion (in MySQL):
WHERE
    (id_v, lang) NOT IN
    (SELECT 
        id_v, lang
    FROM 
        ven_data v2
    ) ;

You can see the whole setup (together with all the steps 1 by 1) and you can experiment at
dbfiddle here

NOTEs: you don't need to do this from a stored procedure, nor you need to use arrays. This code is quite standard SQL. Note that it also works with PostgreSQL  or SQL Server, for instance.