!6 fix build error due to vala upgrade

From: @cherry530 
Reviewed-by: @caodongxia 
Signed-off-by: @caodongxia

create-lists-of-nullable-types.patch

@@ -0,0 +1,33 @@
+From 18beaecbbcc066e0d4c889b3aa3ecaa7351f7768 Mon Sep 17 00:00:00 2001
+From: Evgeny Stambulchik <fnevgeny@gmail.com>
+Date: Tue, 25 Apr 2023 16:11:25 +0300
+Subject: [PATCH] Create Lists of nullable types
+
+---
+ src/classes/drawings/drawing_commands.vala | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/src/classes/drawings/drawing_commands.vala b/src/classes/drawings/drawing_commands.vala
+index 77e56e6d..c305a8c5 100644
+--- a/src/classes/drawings/drawing_commands.vala
++++ b/src/classes/drawings/drawing_commands.vala
+@@ -54,8 +54,8 @@ namespace pdfpc {
+         }
+ 
+         public void clear() {
+-            this.drawing_commands = new List<DrawingCommand>();
+-            this.redo_commands = new List<DrawingCommand>();
++            this.drawing_commands = new List<DrawingCommand?>();
++            this.redo_commands = new List<DrawingCommand?>();
+         }
+ 
+         public void add_line(bool is_eraser,
+@@ -70,7 +70,7 @@ namespace pdfpc {
+ 
+             // After adding a new line you can no longer redo the old
+             // path.
+-            this.redo_commands = new List<DrawingCommand>(); // clear
++            this.redo_commands = new List<DrawingCommand?>(); // clear
+ 
+             bool new_path = true;
+             double epsilon = 1e-4; // Less than 0.1 pixel for a 1000x1000 img

pdfpc.spec

@@ -0,0 +1,73 @@
+Name:           pdfpc
+Version:        4.6.0
+Release:        2
+Summary:        A GTK based presentation viewer application for GNU/Linux
+
+License:        GPL-3.0-or-later
+URL:            https://%{name}.github.io/
+Source0:        https://github.com/%{name}/%{name}/archive/v%{version}.tar.gz
+
+Patch0001:      create-lists-of-nullable-types.patch
+
+BuildRequires:  cmake
+BuildRequires:  gcc
+BuildRequires:  gtk3-devel
+BuildRequires:  gstreamer1-devel
+BuildRequires:  gstreamer1-plugins-base-devel
+BuildRequires:  json-glib-devel
+BuildRequires:  libmarkdown-devel
+BuildRequires:  librsvg2-devel
+BuildRequires:  libgee-devel
+BuildRequires:  pango-devel
+BuildRequires:  poppler-glib-devel
+BuildRequires:  webkit2gtk3-devel
+BuildRequires:  vala vala-devel
+BuildRequires:  qrencode-devel
+
+%description
+pdfpc is a GTK based presentation viewer application for GNU/Linux which uses
+Keynote like multi-monitor output to provide meta information to the speaker
+during the presentation. It is able to show a normal presentation window on one
+screen, while showing a more sophisticated overview on the other one providing
+information like a picture of the next slide, as well as the left over time
+till the end of the presentation. The input files processed by pdfpc are PDF
+documents, which can be created using nearly any of today's presentation
+software.
+
+%prep
+%autosetup -n %{name}-%{version} -p1
+
+%build
+%cmake -DSYSCONFDIR=/etc .
+%make_build
+
+
+%install
+%make_install
+
+
+%files
+%doc README.rst CHANGELOG.rst
+%{_bindir}/%{name}
+%license LICENSE.txt
+%config(noreplace) %{_sysconfdir}/%{name}rc
+%{_mandir}/man1/%{name}*
+%{_mandir}/man5/%{name}*
+%{_datadir}/%{name}
+
+
+%changelog
+* Wed Sep 20 2023 xu_ping <707078654@qq.com> - 4.6.0-2
+- fix build error due to vala upgrade.
+
+* Wed Apr 12 2023 chenchen <chen_aka_jan@163.com> - 4.6.0-1
+- Upgrade pdfpc to 4.6.0
+
+* Tue Jan 04 2022 yaoxin <yaoxin30@huawei.com> - 4.5.0-1
+- Upgrade pdfpc to 4.5.0
+
+* Fri Jul 30 2021 chenyanpanHW <chenyanpan@huawei.com> - 4.3.4-2
+- DESC: delete -S git from %autosetup, and delete BuildRequires git-core
+
+* Tue Nov 17 2020 wangyue <wangyue92@huawei.com> - 4.3.4-1
+- package init

pdfpc.yaml

@@ -0,0 +1,5 @@
+git_url: https://github.com/pdfpc/pdfpc
+version_control: github
+src_repo: pdfpc/pdfpc
+tag_prefix: "^v"
+seperator: "."