[gimp] app: fix check for XCF 14.

[Jehan <jehanp src gnome org>]

commit b8eef4e859f99f7e16903b09776516e0e748cc68
Author: Jehan <jehan girinstud io>
Date:   Tue May 26 16:54:20 2020 +0200

    app: fix check for XCF 14.
    
    I must obvioulsy check for selected layer number over 1, not 0. Right
    now, all common XCF files ended as being version 14.

 app/core/gimpimage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/app/core/gimpimage.c b/app/core/gimpimage.c
index 335d8c3341..f490e310eb 100644
--- a/app/core/gimpimage.c
+++ b/app/core/gimpimage.c
@@ -2818,7 +2818,7 @@ gimp_image_get_xcf_version (GimpImage    *image,
       version = MAX (11, version);
     }
 
-  if (g_list_length (gimp_image_get_selected_layers (image)) > 0)
+  if (g_list_length (gimp_image_get_selected_layers (image)) > 1)
     {
       ADD_REASON (g_strdup_printf (_("Multiple layer selection was "
                                      "added in %s"), "GIMP 2.10.20"));