silence glib log output during fuzzing on oss-fuzz

src/fe-fuzz/null-logger.c

@@ -0,0 +1,16 @@
+#include <irssi/src/fe-fuzz/null-logger.h>
+
+#include <glib.h>
+
+static void null_logger(const gchar *log_domain,
+			GLogLevelFlags log_level,
+			const gchar *message,
+			gpointer user_data)
+{
+	return;
+}
+
+void g_log_set_null_logger(void)
+{
+	g_log_set_default_handler(null_logger, NULL);
+}