[gtksourceview] View: fix assignment from incompatible pointer type

[Sébastien Wilmet <swilmet src gnome org>]

commit b25e71c57fc934a7ce36e51826af9fa7c2cf9a80
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Thu Dec 14 13:03:15 2017 +0100

    View: fix assignment from incompatible pointer type
    
    GLib now propagates types with g_object_ref().
    
    At that code path we are sure that buffer is a GtkSourceBuffer since
    there is a condition if (GTK_SOURCE_IS_BUFFER (buffer)).

 gtksourceview/gtksourceview.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtksourceview/gtksourceview.c b/gtksourceview/gtksourceview.c
index 21424be..e642ce3 100644
--- a/gtksourceview/gtksourceview.c
+++ b/gtksourceview/gtksourceview.c
@@ -1531,7 +1531,7 @@ set_source_buffer (GtkSourceView *view,
        {
                GtkSourceBufferInternal *buffer_internal;
 
-               view->priv->source_buffer = g_object_ref (buffer);
+               view->priv->source_buffer = g_object_ref (GTK_SOURCE_BUFFER (buffer));
 
                g_signal_connect (buffer,
                                  "highlight-updated",