Account for `-1` being returned by `wc_get_page_id()`

[johnbillion]

I've identified a large number of unnecessary database queries being triggered by WooCommerce Germanized, and I traced the problem to the fact that the WooCommerce function wc_get_page_id() can return -1 if a given page does not exist. Germanized doesn't check for this and the result is that if some pages are not configured, for example the "Terms & Conditions" page, Germanized ultimately causes the following database query to be called repeatedly:

SELECT *
FROM wp_posts
WHERE ID = -1
LIMIT 1

This is because wc_gzd_get_page_permalink() does not expect wc_get_page_id() to return -1 and therefore passes it through to get_permalink() which will perform a database query looking for a post with an ID of -1.

Impact

On this particular client site we're seeing this unnecessary query being performed over 25 times on every page load.

To reproduce

• Configure Germanized but don't select any pages on the WooCommerce -> Settings -> Germanized -> General screen
• Install the Query Monitor plugin for debugging purposes
• View a page and observe the unnecessary queries in the Query Monitor -> Queries panel

Results will probably differ on different sites and with a different number of pages either configured or not configured.

Screenshot

[dennisnissle]

Hi @johnbillion,

thanks for the patch and the research, seems fine. I'll merge it.

Best, Dennis