fix(network): prevent null multiplayer peer crashes offline/teardown and fix Nakama RPC session validation

test_suite/tests/socket_simple_test.gd

@@ -0,0 +1,27 @@
+extends "res://base_test.gd"
+
+var _connected = false
+
+func setup():
+	var client = Nakama.create_client(Config.SERVER_KEY, Config.HOST, Config.PORT, Config.SCHEME)
+
+	var session = await client.authenticate_custom_async("MyIdentifier")
+	if assert_cond(session.is_valid()):
+		return
+
+	var socket = Nakama.create_socket_from(client)
+	socket.connected.connect(self._on_socket_connected)
+	var conn = await socket.connect_async(session)
+	# Check that connection succeded
+	if assert_false(conn.is_exception()):
+		return
+	# Check that signal has been called
+	if assert_cond(_connected):
+		return
+	done()
+
+func _on_socket_connected():
+	_connected = true
+
+func _process(_delta):
+	assert_time(3)