PangoAttrList crash

[hugopl]

Generator generated memory management for PangoAttr doesn't work and crash.

require "./spec_helper"

Spec.after_each do
  GC.collect
end

@[NoInline]
def crate_attrlist
  Pango::AttrList.new
end

describe Pango::AttrList do
  it "works" do
    attr_list = crate_attrlist
    attr = Pango.attr_foreground_new(1, 2, 3)
    attr.start_index = 1
    attr.end_index = 7
    attr_list << attr
  end
end

Invalid memory access (signal 11) at address 0x55ad0a16c
[0x55ad08b41d36] *Exception::CallStack::print_backtrace:Nil +118 in /home/hugo/.cache/crystal/crystal-run-spec.tmp
[0x55ad08b2d9c6] ~procProc(Int32, Pointer(LibC::SiginfoT), Pointer(Void), Nil) +310 in /home/hugo/.cache/crystal/crystal-run-spec.tmp
[0x7f8d1fd93ab0] ?? +140244101446320 in /usr/lib/libc.so.6
[0x7f8d20377c46] ?? +140244107623494 in /usr/lib/libpango-1.0.so.0
[0x7f8d20377cb5] pango_attr_list_unref +69 in /usr/lib/libpango-1.0.so.0
[0x55ad08c59cd0] *Pango::AttrList#finalize:Nil +48 in /home/hugo/.cache/crystal/crystal-run-spec.tmp
[0x55ad08b30516] ~proc7Proc(Pointer(Void), Pointer(Void), Nil) +6 in /home/hugo/.cache/crystal/crystal-run-spec.tmp
[0x7f8d1ffc623f] GC_invoke_finalizers +79 in /usr/lib/libgc.so.1

pango_attr_list_unref is causing the fuzz.