[gimp/gimp-2-10] build: add libwmf patch from libwmf repository to prevent issue #4016

[Michael Schumacher <schumaml src gnome org>]

commit 72709161905fa30f49a083f584bc66e926eac38c
Author: Michael Schumacher <schumaml gmx de>
Date:   Sat Jun 13 15:04:24 2020 +0200

    build: add libwmf patch from libwmf repository to prevent issue #4016
    
    (cherry picked from commit 0ce3798a422eec5432a9ae82c7c28ed58398e165)

 ...-libwmf-check-incoming-metric-for-nullptr.patch | 26 ++++++++++++++++++++++
 1 file changed, 26 insertions(+)
---
diff --git a/build/windows/patches/issue-4016-libwmf-check-incoming-metric-for-nullptr.patch 
b/build/windows/patches/issue-4016-libwmf-check-incoming-metric-for-nullptr.patch
new file mode 100644
index 0000000000..1c26e87807
--- /dev/null
+++ b/build/windows/patches/issue-4016-libwmf-check-incoming-metric-for-nullptr.patch
@@ -0,0 +1,26 @@
+From 4ed8f5ee5af8c06ee2ba1fa9017402c9526fa406 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Caol=C3=A1n=20McNamara?= <caolanm redhat com>
+Date: Mon, 24 Feb 2020 09:18:13 +0000
+Subject: [PATCH] check incoming metric for nullptr
+
+https://github.com/caolanm/libwmf/issues/2
+---
+ src/font.c | 5 ++++-
+ 1 file changed, 4 insertions(+), 1 deletion(-)
+
+diff --git a/src/font.c b/src/font.c
+index 6b88499..5b45355 100644
+--- a/src/font.c
++++ b/src/font.c
+@@ -1683,7 +1683,10 @@ static FT_Face ipa_font_face_open (wmfAPI* API,char* ps_name,char* glyphs,char*
+       }
+ 
+ #ifdef _WIN32
+-      metrics = remap_font_file_name (API,metrics);
++      if (metrics)
++      {
++              metrics = remap_font_file_name (API,metrics);
++      }
+ #endif
+       if (metrics)
+       {       if (stat (metrics,&stat_buf))