Fix InputMap and display server not nulling singleton on free

core/input/input_map.cpp

@@ -746,3 +746,7 @@ InputMap::InputMap() {
 	ERR_FAIL_COND_MSG(singleton, "Singleton in InputMap already exist.");
 	singleton = this;
 }
+
+InputMap::~InputMap() {
+	singleton = nullptr;
+}

core/input/input_map.h

@@ -95,6 +95,7 @@ public:
 	const OrderedHashMap<String, List<Ref<InputEvent>>> &get_builtins();
 
 	InputMap();
+	~InputMap();
 };
 
 #endif // INPUT_MAP_H

servers/display_server.cpp

@@ -605,4 +605,5 @@ DisplayServer::DisplayServer() {
 }
 
 DisplayServer::~DisplayServer() {
+	singleton = nullptr;
 }