[gimp] plug-ins: fix wrong return type warning.

[Jehan <jehanp src gnome org>]

commit 97dc1bf9c62e6ef4f349f0de8e158c514d1db883
Author: Jehan <jehan girinstud io>
Date:   Mon Aug 31 12:52:23 2020 +0200

    plug-ins: fix wrong return type warning.
    
    save_image() returns a boolean not a pointer.

 plug-ins/common/file-heif.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/plug-ins/common/file-heif.c b/plug-ins/common/file-heif.c
index 45de152287..cb3cb6dd0b 100644
--- a/plug-ins/common/file-heif.c
+++ b/plug-ins/common/file-heif.c
@@ -1293,7 +1293,7 @@ save_image (GFile                        *file,
     {
       g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
                    "cannot allocate heif_context");
-      return NULL;
+      return FALSE;
     }
 
   g_object_get (config,