String is null

[x-MV]

static 
    String: itemDB_Desc[MAX_ITEMS];

String:GetItemData_Desc(ITEM: itemid)
    return itemDB_Desc[itemid];

ITEM: NewItem(const name[MAX_ITEM_NAME], const SQLname[MAX_ITEM_NAME], const desc[] = "No information", const Float: preview[4], model)
{
    //some working code

    itemDB_Desc[newitem] = str_new(desc);

    return newitem;
}

// creating item
NewItem("Mobile phone", "phone", "Mobile phone description", Float:{0.0, 0.0, 0.0, 1.0}, 18866);

// and code

native ShowPlayerDialogAMXStr(playerid, dialogid, style, caption[], AmxString:info, button1[], button2[]) = ShowPlayerDialog;

// showing dialog
ShowPlayerDialogAMXStr(playerid, dialog_none, DIALOG_STYLE_MSGBOX, "Item information",
GetItemData_Desc(PlayerInventory[playerid][i][INV_ITEMID]), "Okay", "");

// PlayerInventory[playerid][i][INV_ITEMID] gives right value

// also tried

new buffer[128];

str_get(GetItemData_Desc(PlayerInventory[playerid][i][INV_ITEMID]), buffer);
print(buffer);

//prints (null)```

[IS4Code]

If you store a string in a permanent location, you must call str_acquire on it when you add it and str_release when you remove it. Otherwise, the garbage collector will delete it early.