remove Object member from BMesh struct - was only used for undo and BMEditMesh already stores an object pointer.

also fix for own mistake with mesh conversion refactor, shape key index was off by 1 when switching editmode.

source/blender/python/bmesh/bmesh_py_api.c

@@ -59,7 +59,7 @@ static PyObject *bpy_bm_new(PyObject *UNUSED(self))
 {
 	BMesh *bm;
 
-	bm = BM_mesh_create(NULL, &bm_mesh_allocsize_default);
+	bm = BM_mesh_create(&bm_mesh_allocsize_default);
 
 	return BPy_BMesh_CreatePyObject(bm, BPY_BMFLAG_NOP);
 }