MeshTools: don't create reference from rvalue.
MeshTools: don't create reference from rvalue.

Spotted by Emscripten/Clang, not found when running clang normally.

ashimidashajia/magnum,MiUishadow/magnum,DerThorsten/magnum,MiUishadow/magnum,ashimidashajia/magnum,MiUishadow/magnum,DerThorsten/magnum,DerThorsten/magnum,ashimidashajia/magnum,DerThorsten/magnum,MiUishadow/magnum,MiUishadow/magnum,ashimidashajia/magnum,ashimidashajia/magnum,MiUishadow/magnum,DerThorsten/magnum