[gnome-builder] color-picker: don't stop the document monitor on a NULL ref

[Sébastien Lafargue <slafargue src gnome org>]

commit 747b274a3402a55f9f015854f6b3824d4c0770fc
Author: Sebastien Lafargue <slafargue gnome org>
Date:   Fri Sep 8 22:14:36 2017 +0200

    color-picker: don't stop the document monitor on a NULL ref
    
    ide_set_weak_pointer change self->buffer to NULL
    when we close the view, we need to call stop_monitor before.

 .../gb-color-picker-document-monitor.c             |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/plugins/color-picker/gb-color-picker-document-monitor.c 
b/plugins/color-picker/gb-color-picker-document-monitor.c
index a29b793..f7108d0 100644
--- a/plugins/color-picker/gb-color-picker-document-monitor.c
+++ b/plugins/color-picker/gb-color-picker-document-monitor.c
@@ -500,14 +500,15 @@ gb_color_picker_document_monitor_set_buffer (GbColorPickerDocumentMonitor *self,
   g_return_if_fail (GB_IS_COLOR_PICKER_DOCUMENT_MONITOR (self));
   g_return_if_fail (!buffer || IDE_IS_BUFFER (buffer));
 
+  if (self->buffer != buffer && self->buffer != NULL)
+    stop_monitor (self);
+
   if (ide_set_weak_pointer (&self->buffer, buffer))
     {
       g_object_notify_by_pspec (G_OBJECT (self), properties [PROP_BUFFER]);
 
       if (buffer != NULL)
         start_monitor (self);
-      else
-        stop_monitor (self);
     }
 }