[glom/glom-1-30] utils_ui: Don't crash when showing error.

[Murray Cumming <murrayc src gnome org>]

commit 14d914bc56a4d6f3c43c43901e95369de44a62a2
Author: Murray Cumming <murrayc murrayc com>
Date:   Mon May 16 19:13:16 2016 +0200

    utils_ui: Don't crash when showing error.

 glom/utils_ui.cc |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/glom/utils_ui.cc b/glom/utils_ui.cc
index ee4cd06..1bc5358 100644
--- a/glom/utils_ui.cc
+++ b/glom/utils_ui.cc
@@ -66,7 +66,12 @@ static void on_css_parsing_error(const Glib::RefPtr<const Gtk::CssSection>& sect
 
   if(section)
   {
-    std::cerr << " URI = " << section->get_file()->get_uri() << std::endl;
+    const auto file = section->get_file();
+    if (file)
+    {
+      std::cerr << " URI = " << section->get_file()->get_uri() << std::endl;
+    }
+
     std::cerr << " start_line = " << section->get_start_line()+1
       << ", end_line = " << section->get_end_line()+1 << std::endl;
     std::cerr << " start_position = " << section->get_start_position()