[libchamplain] Fix path-layer surface exporting when no clone is visible.

[Jiří Techet <jiritechet src gnome org>]

commit be636b39e1208033850ca65b93ac69c3fab25378
Author: Marius Stanciu <stanciumarius94 gmail com>
Date:   Thu Sep 29 21:39:54 2016 +0300

    Fix path-layer surface exporting when no clone is visible.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=771698

 champlain/champlain-path-layer.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/champlain/champlain-path-layer.c b/champlain/champlain-path-layer.c
index 47956ad..070904f 100644
--- a/champlain/champlain-path-layer.c
+++ b/champlain/champlain-path-layer.c
@@ -842,6 +842,9 @@ update_surface (ChamplainPathLayer *layer,
       cairo_surface_destroy (new_surface);
       cairo_destroy (cr);
     }
+  /* When only the right actor is visible, no merging is required */
+  else if (!CLUTTER_ACTOR_IS_VISIBLE (priv->left_actor))
+    set_surface (CHAMPLAIN_EXPORTABLE (layer), priv->right_surface);
 }
 
 static gboolean