getproperty() for GBoxed type properties is broken

[jwahlstrand]

using Gtk4

c = GtkColorButton()
c.rgba

produces:

ERROR: MethodError: no constructors have been defined for Gtk4.GLib.GBoxed
Stacktrace:
 [1] convert(::Type{Gtk4.GLib.GBoxed}, unbox::Ptr{Gtk4.GLib.GBoxed}, owns::Bool)
   @ Gtk4.GLib ~/Sync/Gtk4.jl/src/GLib/gtype.jl:119
 [2] convert(::Type{Gtk4.GLib.GBoxed}, unbox::Ptr{Gtk4.GLib.GBoxed})
   @ Gtk4.GLib ~/Sync/Gtk4.jl/src/GLib/gtype.jl:119
 [3] (::Gtk4.GLib.var"#70#71")(v::Base.RefValue{Gtk4.GLib.GValue})
   @ Gtk4.GLib ~/Sync/Gtk4.jl/src/GLib/gvalues.jl:186
 [4] getindex(gv::Base.RefValue{Gtk4.GLib.GValue}, ::Type{Any})
   @ Gtk4.GLib ~/Sync/Gtk4.jl/src/GLib/gvalues.jl:247
 [5] get_gtk_property(w::GtkColorButtonLeaf, name::String)
   @ Gtk4.GLib ~/Sync/Gtk4.jl/src/GLib/gvalues.jl:289
 [6] get_gtk_property
   @ ~/Sync/Gtk4.jl/src/GLib/gvalues.jl:284 [inlined]
 [7] getproperty(w::GtkColorButtonLeaf, name::Symbol)
   @ Gtk4.GLib ~/Sync/Gtk4.jl/src/GLib/gvalues.jl:353
 [8] top-level scope
   @ REPL[3]:1

As a workaround, use the accessor method:

Gtk4.rgba(c)