Fix bug in MockMesh and MockTriangleMesh ::getVertexNormal. The const ref being returned was to the normal in a copy of the data that goes out of scope.
Fix bug in MockMesh and MockTriangleMesh ::getVertexNormal.
The const ref being returned was to the normal in a copy of the data that goes out of scope.

simquest/opensurgsim,simquest/opensurgsim,simquest/opensurgsim,simquest/opensurgsim