Reproduction steps:
1. Download project "TestProject.zip" and open in Unity
2. Open scene "testscene"
3. Enter Play mode

Expected: SkinnedMeshRenderer property sharedMesh should be initialized
Actual: code line "newSkinnedMeshRenderer.sharedMesh = new Mesh();" triggers error in Unity console:
"SkinnedMeshRenderer: Trying to set a mesh ("") that is unfit for use with SkinnedMeshRenderer. Most likely it doesn't have Skin information and/or is only assigned to the renderer during runtime, in which case Unity isn't aware of its use with SkinnedMeshRenderer. Mark the mesh as Readable or assign it to the renderer in the Editor before building.
UnityEngine.SkinnedMeshRenderer:set_sharedMesh(Mesh)"

Reproduced on: 2017.1.0p4; 2017.1.1f1; 2017.2.0b9; 2017.3.0a6
Not reproduced on: 5.5.4p4; 5.6.3p2; 2017.1.0f3; 2017.1.0p3
Regression started: 2017.1.0p4

Fixed on: 5.6.3p3; 2017.1.1f1