"ERROR: FATAL: Condition "!rc_owner" is true." on close after using GetThemeStylebox in C#

[kevicency]

Tested versions

4.3-dev.6

System information

Godot v4.3.dev6.mono - macOS 14.4.1 - Vulkan (Forward+) - integrated Apple M2 Max - Apple M2 Max (12 Threads)

Issue description

After working on an inventory system which made heavy use of PanelContainer and StyleBoxFlat i ran into the problem where my game and the editor threw an error on close (ERROR: FATAL: Condition "!rc_owner" is true.) and the process had to be manually killed every time.

I was able to somewhat isolate the issue in an MRP but in my actual project there are more issues that i couldn't reproduce. F.e. i have a custom control which extends PanelContainer but as soon a i set a theme overwrite for the panel style box in the editor and start the game / close the editor i get the same error and the editor hangs on close (even without any code accessing the style box overwrite)

Steps to reproduce

• Remove style panel override in MyPanelContainer in MRP (https://github.com/kevicency/godot-issue_stylebox/blob/main/MyPanelContainer.tscn#L8)
• Run game
• Try to close it

Minimal reproduction project (MRP)

https://github.com/kevicency/godot-issue_stylebox/blob/main/MyPanelContainer.cs

[AThousandShips]

Sounds like:

• Godot mono - Crash on app shutdown: Condition "!rc_owner" is true. OR signal 11 on MacOS #89188

[kevicency]

Yes i saw that issue and it's probably related but i don't have any audio in my game yet

[matheusmdx]

I tried to reproduce the issue but nothing happens here:

unknown_2024.05.18-08.46.mp4

My specs: Godot v4.3.dev6.mono - Windows 10.0.19045 - Vulkan (Forward+) - dedicated AMD Radeon RX 580 2048SP (Advanced Micro Devices, Inc.; 31.0.21912.14) - AMD Ryzen 5 3600 6-Core Processor (12 Threads)

[kevicency]

@matheusmdx i think it only happens on macOS. i just also tried to reproduce it on my win desktop but i also didn't get the error

[knightofiam]

Related to #83973, #89188.