TriangleMeshSlicer is now initialized by const-pointer to the mesh, responsibility for calling require_shared_vertices is left to the caller

src/libslic3r/SLA/SLABasePool.cpp

@@ -552,6 +552,7 @@ void base_plate(const TriangleMesh &mesh, ExPolygons &output, float h,
                 float layerh, ThrowOnCancel thrfn)
 {
     TriangleMesh m = mesh;
+    m.require_shared_vertices(); // TriangleMeshSlicer needs this
     TriangleMeshSlicer slicer(&m);
 
     auto bb = mesh.bounding_box();

src/libslic3r/SLA/SLASupportTree.cpp

@@ -2231,6 +2231,7 @@ SlicedSupports SLASupportTree::slice(float layerh, float init_layerh) const
 
     TriangleMesh fullmesh = m_impl->merged_mesh();
     fullmesh.merge(get_pad());
+    fullmesh.require_shared_vertices(); // TriangleMeshSlicer needs this
     TriangleMeshSlicer slicer(&fullmesh);
     SlicedSupports ret;
     slicer.slice(heights, 0.f, &ret, get().ctl().cancelfn);
@@ -2243,6 +2244,7 @@ SlicedSupports SLASupportTree::slice(const std::vector<float> &heights,
 {
     TriangleMesh fullmesh = m_impl->merged_mesh();
     fullmesh.merge(get_pad());
+    fullmesh.require_shared_vertices(); // TriangleMeshSlicer needs this
     TriangleMeshSlicer slicer(&fullmesh);
     SlicedSupports ret;
     slicer.slice(heights, cr, &ret, get().ctl().cancelfn);