[gimp] plug-ins: set appropriate status when file-heif's load_image() fails.

[Jehan Pagès <jehanp src gnome org>]

commit 05145f44f23a43103f0f4028595545cf4a95e259
Author: Jehan <jehan girinstud io>
Date:   Fri May 11 22:44:00 2018 +0200

    plug-ins: set appropriate status when file-heif's load_image() fails.
    
    Current code was only taking into account cancelation, so we could end
    with weird plug-in return:
    
    > HEIF/HEIC plug-in returned SUCCESS but did not return an image
    
    Instead properly set an error status, and echo back the error from the
    plug-in or libheif.

 plug-ins/common/file-heif.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/plug-ins/common/file-heif.c b/plug-ins/common/file-heif.c
index 43a857e..3fe86d0 100644
--- a/plug-ins/common/file-heif.c
+++ b/plug-ins/common/file-heif.c
@@ -194,6 +194,10 @@ run (const gchar      *name,
             {
               status = GIMP_PDB_CANCEL;
             }
+          else
+            {
+              status = GIMP_PDB_CALLING_ERROR;
+            }
         }
 
       g_object_unref (file);