display error of non-english string in flet app of Raspberry pi.

[racuca]

hello.
I am installing bullseye OS on Raspberry Pi CM4 and coding a flet app.
OS info.
Release date: May 3rd 2023
System: 64-bit
Kernel version: 6.1
Debian version: 11 (bullseye)

I set Korean language settings during installation, and Korean language is displayed well on the OS.
The problem is that when I run the flet app, the English language is displayed fine, but the Korean language is not displayed properly and is displayed as a square box.
What is unusual is that not all letters are broken, but the Korean language in the title is displayed normally.
The flet version is 0.11.0, but the same thing happens if you install another lower version - for example 0.7.1.
How can I display Korean properly in all controls?
Below, I attach the modified source code and execution photo of the clickable-container.py example.

`import flet as ft

def main(page: ft.Page):
page.title = "콘테이너 Containers - clickable and not"
page.vertical_alignment = ft.MainAxisAlignment.CENTER
page.horizontal_alignment = ft.CrossAxisAlignment.CENTER

page.add(
    ft.Row(
        [
            ft.Container(
                content=ft.Text("클릭안됨 Non clickable"),
                margin=10,
                padding=10,
                alignment=ft.alignment.center,
                bgcolor=ft.colors.AMBER,
                width=150,
                height=150,
                border_radius=10,
            ),
            ft.Container(
                content=ft.Text("Clickable without Ink"),
                margin=10,
                padding=10,
                alignment=ft.alignment.center,
                bgcolor=ft.colors.GREEN_200,
                width=150,
                height=150,
                border_radius=10,
                on_click=lambda e: print("Clickable without Ink clicked!"),
            ),
            ft.Container(
                content=ft.Text("Clickable with Ink"),
                margin=10,
                padding=10,
                alignment=ft.alignment.center,
                bgcolor=ft.colors.CYAN_200,
                width=150,
                height=150,
                border_radius=10,
                ink=True,
                on_click=lambda e: print("Clickable with Ink clicked!"),
            ),
            ft.Container(
                content=ft.Text("Clickable transparent with Ink"),
                margin=10,
                padding=10,
                alignment=ft.alignment.center,
                width=150,
                height=150,
                border_radius=10,
                ink=True,
                on_click=lambda e: print("Clickable transparent with Ink clicked!"),
            ),
        ],
        alignment=ft.MainAxisAlignment.CENTER,
    ),
)

ft.app(target=main)
`

[racuca]

I found the problem.
font was missed.
So I added page.font with ttf files manually.
But I have no idea why font problem happens.