Creating a custom layout with 6 rows throws an error

[Aaron Wells]

To replicate:

1. Edit a page
2. Go to the Layout tab
3. Expand "Advanced options"
4. Click on "Custom layout"
5. Keep clicking "Add row" until you have 6 rows
6. Click "Create layout"
7. Click "Save"

Expected result: The page has a custom layout with 6 rows
Actual result: You see an error page with this error message:

[WAR] 56 (lib/view.php:2439) [[invalidnumrows/error]]
Call stack (most recent first):

    View->addrow(array(size 3)) at /home/aaronw/www/mahara/htdocs/view/layout.php:249
    viewlayout_submit(object(Pieform), array(size 5)) at Unknown:0
    call_user_func_array("viewlayout_submit", array(size 2)) at /home/aaronw/www/mahara/htdocs/lib/pieforms/pieform.php:528
    Pieform->__construct(array(size 6)) at /home/aaronw/www/mahara/htdocs/lib/pieforms/pieform.php:170
    Pieform::process(array(size 6)) at /home/aaronw/www/mahara/htdocs/lib/pieforms/pieform.php:71
    pieform(array(size 6)) at /home/aaronw/www/mahara/htdocs/view/layout.php:171

[Aaron Wells (u-aaronw)]

This was spun off from https://bugs.launchpad.net/mahara/+bug/1236767

Actually, there's a second bug here as well, which is the missing lang string "invalidnumrows/error"

[Aaron Wells (u-aaronw)]

https://reviews.mahara.org/2597

[Aaron Wells (u-aaronw)]

A second patch for the lang string: https://reviews.mahara.org/2598