Unable to find availability of more than one room

Problem/Motivation

When number rooms > 1 the availability search redirects the user to a /booking page with an empty search form with message text: "Perform a search to get availability information"

Note that there are no results, even if there are plenty of rooms available during the date range specified

Steps to reproduce:

1. Ensure rooms is configured to show individual units on availability search, and that you have at least two unit types and one room for each type.
2. Visit /booking page (or any page that contains the availability search form).
3. Select a date range a few months in the future where there are guaranteed to be rooms available, and specify 2 rooms, 2 guests.
4. Click search button, to open availability search results page.

Proposed resolution

1. If there are results to be found (there should be results!) a search result page should be shown.
2. If no results then, at the very least, an appropriate warning / error message should be shown indicating that there were no rooms available and the user should widen their search.
3. Ideally, also if no results, then the user would be re-routed back to the /booking page and the form values entered by the user should be pre-filled in the form.

Remaining tasks

Write code.

User interface changes

None.

API changes

None.

Original report by @dialn

When the number of rooms> 1 is selected no results only the following message, no matter the number of rooms field if it will not work with a number> 1