[gnome-flashback] shell: use g_strcmp0 which is null safe, instead of g_str_equal

[Alberts Muktupāvels <muktupavels src gnome org>]

commit bd970ecf9cbebebcabc8befad2df83132a1920c4
Author: Dmitry Shachnev <mitya57 gmail com>
Date:   Thu Oct 11 19:32:56 2018 +0300

    shell: use g_strcmp0 which is null safe, instead of g_str_equal
    
    https://gitlab.gnome.org/GNOME/gnome-flashback/issues/13

 gnome-flashback/libshell/flashback-shell.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gnome-flashback/libshell/flashback-shell.c b/gnome-flashback/libshell/flashback-shell.c
index 47136fb..f3ffa09 100644
--- a/gnome-flashback/libshell/flashback-shell.c
+++ b/gnome-flashback/libshell/flashback-shell.c
@@ -377,7 +377,7 @@ handle_ungrab_accelerator (FlashbackDBusShell    *dbus_shell,
   sender = (gchar *) g_hash_table_lookup (shell->grabbed_accelerators,
                                           GUINT_TO_POINTER (action));
 
-  if (g_str_equal (sender, g_dbus_method_invocation_get_sender (invocation)))
+  if (g_strcmp0 (sender, g_dbus_method_invocation_get_sender (invocation)) == 0)
     {
       success = real_ungrab (shell, action);