“ The defendants, other than the trustees, filed a plea to the jurisdiction, alleging that the trustees, 'who are alleged to hold the legal title of the property described and involved, are indispensable parties complainant, and yet, as these defendants aver, those persons are improperly and collusively joined as defendants for the purpose of creating a case cognizable in this honorable court;' and it was also asserted that parties had been improperly and collusively omitted for the same purpose. ”