i3-save-tree: retain “rect” for floating_cons

i3-save-tree

@@ -99,6 +99,7 @@ my %allowed_keys = map { ($_, 1) } qw(
     geometry
     window_properties
     mark
+    rect
 );
 
 sub strip_containers {
@@ -116,6 +117,9 @@ sub strip_containers {
 
     delete $tree->{geometry} if zero_rect($tree->{geometry});
 
+    # Retain the rect for floating containers to keep their positions.
+    delete $tree->{rect} unless $tree->{type} eq 'floating_con';
+
     delete $tree->{current_border_width} if $tree->{current_border_width} == -1;
 
     for my $key (keys %$tree) {