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 */
><td class='form'><form class='right' method='get' action='/guix/log/tests/sets.scm'>
<input type='hidden' name='id' value='f6e06e8b15d1fa6c17d8fd21f95b26985b4e1674'/><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=f6e06e8b15d1fa6c17d8fd21f95b26985b4e1674'>root</a>/<a href='/guix/log/tests?id=f6e06e8b15d1fa6c17d8fd21f95b26985b4e1674'>tests</a>/<a href='/guix/log/tests/sets.scm?id=f6e06e8b15d1fa6c17d8fd21f95b26985b4e1674'>sets.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/tests/sets.scm?id=f6e06e8b15d1fa6c17d8fd21f95b26985b4e1674&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
mmit message (<a href='/guix/log/gnu/tests/databases.scm?id=ba1727b0410326d4cd90eb7236d5539abaff8c67&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-10-18 01:12:22 +0200'>2018-10-18</span></td><td><a href='/guix/commit/gnu/tests/databases.scm?id=39d7fdce453b0ca23ecbed72048647debbaa58a6'>services: dhcp-client: Deprecate 'dhcp-client-service' procedure.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-03-10 16:20:55 +0000'>2018-03-10</span></td><td><a href='/guix/commit/gnu/tests/databases.scm?id=69f7cf2bf4ca3ab792438a9e7fb46f78ef0f227a'>tests: databases: Add a system test for PostgreSQL.</a><span class='msg-avail'>...</span></td><td>Christopher Baines</td></tr>
<tr><td><span title='2017-10-08 17:31:49 +0100'>2017-10-08</span></td><td><a href='/guix/commit/gnu/tests/databases.scm?id=02bc41c4cedd15c6a76ecd5218f9b5848de8baea'>tests: databases: Add a simple test for MySQL.</a><span class='msg-avail'>...</span></td><td>Christopher Baines</td></tr>
<tr><td><span title='2017-10-06 21:24:30 +0100'>2017-10-06</span></td><td><a href='/guix/commit/gnu/tests/databases.scm?id=5266ff719e274056cb3e2b9740183f0063177255'>services: Add MongoDB.</a><span class='msg-avail'>...</span></td><td>Christopher Baines</td></tr>
<tr><td><span title='2017-08-15 22:24:15 +0100'>2017-08-15</span></td><td><a href='/guix/commit/gnu/tests/databases.scm?id=6230e155afd8c43c12ee3f03032aac34433db11a'>gnu: Fix memcached service startup.</a><span class='msg-avail'>...</span></td><td>Christopher Baines</td></tr>
<tr><td><span title='2017-07-30 09:08:30 +0100'>2017-07-30</span></td><td><a href='/guix/commit/gnu/tests/databases.scm?id=119fdd0d0e33492ef2b563295fe9564258d51401'>services: Add memcached.</a><span class='msg-avail'>...</span></td><td>Christopher Baines</td></tr>