[gegl] ff-save: report to stderr on header writing problems

[Øyvind Kolås <ok src gnome org>]

commit 2963c2aab8b2b3298677bcfd1a0255299ae7421b
Author: Øyvind Kolås <pippin gimp org>
Date:   Tue Feb 16 11:49:40 2016 +0100

    ff-save: report to stderr on header writing problems

 operations/external/ff-save.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/operations/external/ff-save.c b/operations/external/ff-save.c
index 2b9fe9d..3655659 100644
--- a/operations/external/ff-save.c
+++ b/operations/external/ff-save.c
@@ -935,7 +935,11 @@ tfile (GeglProperties *o)
       return -1;
     }
 
-  avformat_write_header (p->oc, NULL);
+  if (avformat_write_header (p->oc, NULL) < 0)
+  {
+    fprintf (stderr, "'%s' error writing header\n", o->path);
+    return -1;
+  }
   return 0;
 }