Fix 'Navigation Process' monitor initialization

main/performance.cpp

@@ -316,6 +316,7 @@ uint64_t Performance::get_monitor_modification_time() {
 Performance::Performance() {
 	_process_time = 0;
 	_physics_process_time = 0;
+	_navigation_process_time = 0;
 	_monitor_modification_time = 0;
 	singleton = this;
 }