Expected Behavior

Set the App

Current Behavior

Only installed (without data) and go to the settings page
Impossible to save anything and navigate (Only return back with navigator <-)

Possible Solution

Where is defined $custom_fields['ip_invoice_custom'] ?

Steps to Reproduce

1. Install and login
2. go to index.php/settings

Context (Environment)

New install without data

Possible Implementation (Hard fix)

In application/modules/email_templates/views/template-tags-invoices.php line 48

            <?php foreach ($custom_fields['ip_invoice_custom'] as $custom) { ?>

Add if(isset())

            <?php if(isset($custom_fields['ip_invoice_custom'])) foreach ($custom_fields['ip_invoice_custom'] as $custom) { ?>

Failure Logs

See source (Ctrl+u)
you found an errors like: https://pastebin.com/TvDrhskr