[gnome-builder] history: be safer about buffer/mark access

[Christian Hergert <chergert src gnome org>]

commit 1af0fec8f9a55ceab52aa18c1f3fa5229704a64b
Author: Christian Hergert <chergert redhat com>
Date:   Tue Sep 5 19:34:52 2017 -0700

    history: be safer about buffer/mark access

 plugins/history/gbp-history-item.c |   15 +++++++++++++--
 1 files changed, 13 insertions(+), 2 deletions(-)
---
diff --git a/plugins/history/gbp-history-item.c b/plugins/history/gbp-history-item.c
index 3e4bc8a..f1ce4a4 100644
--- a/plugins/history/gbp-history-item.c
+++ b/plugins/history/gbp-history-item.c
@@ -102,12 +102,15 @@ gboolean
 gbp_history_item_chain (GbpHistoryItem *self,
                         GbpHistoryItem *other)
 {
+  GtkTextBuffer *buffer;
+
   g_return_val_if_fail (GBP_IS_HISTORY_ITEM (self), FALSE);
   g_return_val_if_fail (GBP_IS_HISTORY_ITEM (other), FALSE);
 
-  if (gtk_text_mark_get_buffer (self->mark) == gtk_text_mark_get_buffer (other->mark))
+  if (self->mark != NULL && other->mark != NULL &&
+      NULL != (buffer = gtk_text_mark_get_buffer (self->mark)) &&
+      buffer == gtk_text_mark_get_buffer (other->mark))
     {
-      GtkTextBuffer *buffer = gtk_text_mark_get_buffer (self->mark);
       GtkTextIter self_iter;
       GtkTextIter other_iter;
 
@@ -119,6 +122,14 @@ gbp_history_item_chain (GbpHistoryItem *self,
         return TRUE;
     }
 
+  if (self->file != NULL &&
+      other->file != NULL &&
+      g_file_equal (self->file, other->file))
+    {
+      if (ABS ((gint)self->line - (gint)other->line) < DISTANCE_LINES_THRESH)
+        return TRUE;
+    }
+
   return FALSE;
 }