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

scripts/nakama_manager.gd

@@ -196,6 +196,7 @@ func host_game(room_meta: Dictionary = {}):
 	if bridge.match_state == NakamaMultiplayerBridge.MatchState.CONNECTED:
 		print("[NakamaManager] Already hosting a match; ignoring duplicate host request.")
 		return
+		
 	if bridge.match_state != NakamaMultiplayerBridge.MatchState.DISCONNECTED:
 		# Stranded mid-join (e.g. previous attempt never resolved). Reset so the
 		# bridge is idle before we try again.
@@ -203,8 +204,9 @@ func host_game(room_meta: Dictionary = {}):
 		await bridge.leave()
 
 	print("Hosting match via Nakama Bridge...")
-	await bridge.create_match()
-	# Store room metadata in Nakama storage so other players can see it in listings
+	var result = await bridge.create_match()
+	if result and result.is_exception():
+		emit_signal("match_join_error", result.get_exception().message)
 	if session and current_match_id and room_meta.size() > 0:
 		var meta_json = JSON.stringify(room_meta)
 		var write_obj = NakamaWriteStorageObject.new(