GEOSSTRtree_remove behaviour change in 3.10?

[dark-panda]

I am currently upgrading my ffi-geos Ruby gem (https://github.com/dark-panda/ffi-geos) for 3.10 compatibility and ran across a failing test involving GEOSSTRtree_remove. The test is effectively the following (forgive the Ruby code, but this should be hopefully fairly straight forward):

def test_remove
  @tree = Geos::STRtree.new(3)
  @item_1 = { item_1: :test }
  @item_2 = [:test]
  @item_3 = Object.new

  @geom_1 = read('LINESTRING(0 0, 10 10)')
  @geom_2 = read('LINESTRING(20 20, 30 30)')
  @geom_3 = read('LINESTRING(20 20, 30 30)')

  @tree.insert(@geom_1, @item_1)
  @tree.insert(@geom_2, @item_2)
  @tree.insert(@geom_3, @item_3)

  @tree.remove(read('POINT (5 5)'), @item_1)

  assert_equal([],
    @tree.query(read('LINESTRING(5 5, 6 6)')))

  assert_equal([],
    @tree.query(read('LINESTRING(20 0, 30 10)')))

  assert_equal([@item_2, @item_3],
    @tree.query(read('LINESTRING(25 25, 26 26)')))

  assert_equal([@item_2, @item_3],
    @tree.query(read('LINESTRING(0 0, 100 100)')))
end

In 3.9 and prior, the line for @tree.remove(read('POINT (5 5)'), @item_1) correctly removes the item from the tree and the tests succeed. In 3.10 and in main, the tests fail because the item is not removed.

I noticed there is no test coverage for GEOSSTRtree_remove, which is what I base most of my Ruby tests for new code on, so I'm unsure if I'm correctly implementing Geos::STRtree#remove in my Ruby gem, although it has worked up until this point. When I debug the GEOS code via llvm, I'm noticing that it's bailing out at this point:

https://github.com/libgeos/geos/blob/main/include/geos/index/strtree/TemplateSTRtree.h#L309

bool remove(const BoundsType& itemEnv, const ItemType& item) {
  if (root == nullptr) { // the root is a nullptr coming from my Ruby code
    return false;
  }

Is there something amiss with the implementation or something that needs doing in my Ruby code, or has there been a behaviour change that would affect GEOSSTRtree_remove? At a minimum, I believe there may be a missing regression test for GEOSSTRtree_remove specifically, as there are no references to it outside of the capi/ directory.

The code for my implementation of Geos::STRtree#remove can be found here:

https://github.com/dark-panda/ffi-geos/blob/master/lib/ffi-geos/strtree.rb#L98