Strict warning: Only variables should be passed by reference in rooms_booking.availability_agent.inc

Problem/Motivation

Trying to verify availability of a specific room, if error_reporting on your web server is set to E_ALL (development recomended configuration), the strict warnig message Strict warning: Only variables should be passed by reference in AvailabilityAgent->searchForAvailability() (line 70 of /sites/all/modules/rooms/modules/rooms_booking/includes/rooms_booking.availability_agent.inc)., will be reported

Proposed resolution

Define a varible and pass it to the function requires parameter passed by reference.
Work done in the patch attached.

Remaining tasks

Verify the presence of similar behaviours in other functions/methods around the project.