Fix move of temporary object
Fix move of temporary object

Moving a temporary object prevents copy elision (-Wpessimizing-move).

bkircher/ews-cpp,otris/ews-cpp,otris/ews-cpp,bkircher/ews-cpp,otris/ews-cpp,m-Schlitzer/ews-cpp,bkircher/ews-cpp,otris/ews-cpp,m-Schlitzer/ews-cpp,m-Schlitzer/ews-cpp