Fix the build with gtkmm 4:

https://github.com/transmission/transmission/issues/6392

Patch copied from upstream source repository:

https://github.com/transmission/transmission/commit/e116672b27b314d54514c96b1fa7aef1dee900b1

From e116672b27b314d54514c96b1fa7aef1dee900b1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C5=93ur?= <coeur@gmx.fr>
Date: Sun, 17 Dec 2023 16:37:35 +0100
Subject: [PATCH] fix: build error on  GTKMM-4 (#6393)

---
 gtk/OptionsDialog.cc | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/gtk/OptionsDialog.cc b/gtk/OptionsDialog.cc
index 08198540c10..8c28fc76f98 100644
--- a/gtk/OptionsDialog.cc
+++ b/gtk/OptionsDialog.cc
@@ -338,7 +338,16 @@ void TorrentFileChooserDialog::onOpenDialogResponse(int response, Glib::RefPtr<S
         bool const do_prompt = get_choice(std::string(ShowOptionsDialogChoice)) == "true";
         bool const do_notify = false;
 
-        auto const files = IF_GTKMM4(get_files2, get_files)();
+#if GTKMM_CHECK_VERSION(4, 0, 0)
+        auto files = std::vector<Glib::RefPtr<Gio::File>>();
+        auto files_model = get_files();
+        for (auto i = guint{ 0 }; i < files_model->get_n_items(); ++i)
+        {
+            files.push_back(gtr_ptr_dynamic_cast<Gio::File>(files_model->get_object(i)));
+        }
+#else
+        auto const files = get_files();
+#endif
         g_assert(!files.empty());
 
         /* remember this folder the next time we use this dialog */
cm?id=989d564f4434c6e43df7ccb0d1701e89e243e404'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/busybox.scm'>
<input type='hidden' name='id' value='989d564f4434c6e43df7ccb0d1701e89e243e404'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=989d564f4434c6e43df7ccb0d1701e89e243e404'>root</a>/<a href='/guix/log/gnu?id=989d564f4434c6e43df7ccb0d1701e89e243e404'>gnu</a>/<a href='/guix/log/gnu/packages?id=989d564f4434c6e43df7ccb0d1701e89e243e404'>packages</a>/<a href='/guix/log/gnu/packages/busybox.scm?id=989d564f4434c6e43df7ccb0d1701e89e243e404'>busybox.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/busybox.scm?id=989d564f4434c6e43df7ccb0d1701e89e243e404&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-12-01 00:49:13 +0100'>2019-12-01</span></td><td><a href='/guix/commit/gnu/packages/busybox.scm?id=111f7c017595ac5cf2328a12bad6e8885713fd64'>gnu: toybox: Update to 0.8.2.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-06-17 16:27:16 +0300'>2019-06-17</span></td><td><a href='/guix/commit/gnu/packages/busybox.scm?id=505459d7cb139eaa3b73b4977d502a3acc400b3b'>gnu: busybox: Don't install to usr.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2019-06-17 10:02:45 +0300'>2019-06-17</span></td><td><a href='/guix/commit/gnu/packages/busybox.scm?id=ee0b4733e1a186048983ac6b6ba0bae23b3f567d'>gnu: toybox: Don't install files to usr.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2019-06-06 05:59:00 +0200'>2019-06-06</span></td><td><a href='/guix/commit/gnu/packages/busybox.scm?id=fcc7fa472b111e0916d96621bbf68f869358bdd9'>gnu: toybox: Update to 0.8.1.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-02-17 03:37:50 +0100'>2019-02-17</span></td><td><a href='/guix/commit/gnu/packages/busybox.scm?id=51e31aa865e5d1b272673ae94e13ffdc9f4db536'>gnu: toybox: Update to 0.8.0.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-12-12 09:27:17 +0200'>2018-12-12</span></td><td><a href='/guix/commit/gnu/packages/busybox.scm?id=42140fd434a333d0565617471b51323d6815ee13'>gnu: Add toybox.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>