[easytag] Add an invariant in Log_Print()

[David King <davidk src gnome org>]

commit 8d099a706d1fa8eb67669cca31a44ac7444195a9
Author: David King <amigadave amigadave com>
Date:   Wed Dec 24 15:00:29 2014 +0000

    Add an invariant in Log_Print()
    
    Return and log a critical message if EtLogArea has not been initialized
    when calling Log_Print().

 src/log.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/log.c b/src/log.c
index 83422ba..07b67d6 100644
--- a/src/log.c
+++ b/src/log.c
@@ -296,6 +296,9 @@ Log_Print (EtLogAreaKind error_type, const gchar * const format, ...)
     GError *error = NULL;
 
     self = ET_LOG_AREA (et_application_window_get_log_area (ET_APPLICATION_WINDOW (MainWindow)));
+
+    g_return_if_fail (self != NULL);
+
     priv = et_log_area_get_instance_private (self);
 
     va_start (args, format);