Region "+" skips shapes with user properties on second input

[klayoutmatthias]

For details see this discussion: https://www.klayout.de/forum/discussion/2286/bug-in-klayout-0-28-7-when-doing-cell-by-cell-or-operation-on-shapes-with-user-properties#latest

The code to reproduce the problem is this

the_layout = pya.CellView.active().layout() 
the_cell = pya.CellView.active().cell

l10 = the_layout.layer(10, 0)
the_layout.clear_layer(l10)

for cell in the_layout.each_cell():
    r1 = pya.Region(cell.shapes(the_layout.layer(1, 0) ) )
    r2 = pya.Region(cell.shapes(the_layout.layer(2, 0) ) )
    cell.shapes(l10).insert(r1 + r2 )

Test data is attached.

discussion_2286.gds.zip