[gnome-system-monitor] Use gtk-defined style constant for lsof search error

[Robert Roth <robertroth src gnome org>]

commit 28889a2979060e8da8170577541c1bf3e5be649e
Author: Robert Roth <robert roth off gmail com>
Date:   Sun Mar 15 17:19:23 2015 +0200

    Use gtk-defined style constant for lsof search error

 src/lsof.cpp |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/lsof.cpp b/src/lsof.cpp
index 6f161c1..869cef5 100644
--- a/src/lsof.cpp
+++ b/src/lsof.cpp
@@ -170,11 +170,11 @@ namespace
 
             if (regex_error && !this->regex_error_displayed) {
                 this->regex_error_displayed = true;
-                gtk_style_context_add_class(gtk_widget_get_style_context(GTK_WIDGET(entry)), "error");
+                gtk_style_context_add_class(gtk_widget_get_style_context(GTK_WIDGET(entry)), 
GTK_STYLE_CLASS_ERROR);
             }
             else if (!regex_error && this->regex_error_displayed) {
                 this->regex_error_displayed = false;
-                gtk_style_context_remove_class(gtk_widget_get_style_context(GTK_WIDGET(entry)), "error");
+                gtk_style_context_remove_class(gtk_widget_get_style_context(GTK_WIDGET(entry)), 
GTK_STYLE_CLASS_ERROR);
             }
         }