[gitg] Do not hang on highlighting commit message

[Jesse van den Kieboom <jessevdk src gnome org>]

commit 28b203e3a25e69f90ae6f0867d908eae25d16dea
Author: Jesse van den Kieboom <jessevdk gnome org>
Date:   Sun Jan 10 13:27:12 2016 +0100

    Do not hang on highlighting commit message
    
    Fixes https://bugzilla.gnome.org/show_bug.cgi?id=760376.

 gitg/commit/gitg-commit-dialog.vala |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)
---
diff --git a/gitg/commit/gitg-commit-dialog.vala b/gitg/commit/gitg-commit-dialog.vala
index 7223c45..2d3eaab 100644
--- a/gitg/commit/gitg-commit-dialog.vala
+++ b/gitg/commit/gitg-commit-dialog.vala
@@ -743,8 +743,15 @@ class Dialog : Gtk.Dialog
                                        break;
                                }
 
-                               toolong.backward_line();
-                               toolong.forward_to_line_end();
+                               if (!toolong.backward_line())
+                               {
+                                       break;
+                               }
+                               
+                               if (!toolong.forward_to_line_end())
+                               {
+                                       break;
+                               }
                        }
                }