### Godot version

4.0 RC1

### System information

Linux Mint 20.3 Cinnamon

### Issue description

Tried converting a 3.5 game to 4.0 RC1. The conversion popup menu closed after a few seconds, and trying to edit the game crashes the entire engine with the following errors, which seem to be related to one music file not loading:
![errors](https://user-images.githubusercontent.com/125468288/219127087-f5a78035-4e4a-4625-aadb-e0cde6d5ac3d.png)

Not sure what's causing the issue, because when I created a new project with only that file and converted it I didn't get these errors, but consistently get them when trying to convert that game.

### Steps to reproduce

- Download the reproduction project below
- Import in Godot 4.0, and click "convert full project"
- If the bug happens, the engine will crash whenever trying to edit or run the converted project

### Minimal reproduction project

[Music Convertor Crash Demo.zip](https://github.com/godotengine/godot/files/10746591/Music.Convertor.Crash.Demo.zip)

rename_gdscript_functions(source_lines, reg_container, true); 
				rename_common(RenamesMap3To4::project_settings_renames, reg_container.project_settings_regexes, source_lines);
				rename_gdscript_keywords(source_lines, reg_container, true);
				rename_common(RenamesMap3To4::gdscript_properties_renames, reg_container.gdscript_properties_regexes, source_lines);
				rename_common(RenamesMap3To4::gdscript_signals_renames, reg_container.gdscript_signals_regexes, source_lines);
				rename_common(RenamesMap3To4::shaders_renames, reg_container.shaders_regexes, source_lines);
				rename_common(RenamesMap3To4::builtin_types_renames, reg_container.builtin_types_regexes, source_lines);
				rename_common(RenamesMap3To4::theme_override_renames, reg_container.theme_override_regexes, source_lines);
				custom_rename(source_lines, "\\.shader", ".gdshader");
			} else if (file_name.ends_with(".cs")) { 
				rename_classes(source_lines, reg_container); 
				rename_common(RenamesMap3To4::csharp_function_renames, reg_container.csharp_function_regexes, source_lines);
				rename_common(RenamesMap3To4::builtin_types_renames, reg_container.builtin_types_regexes, source_lines);
				rename_common(RenamesMap3To4::csharp_properties_renames, reg_container.csharp_properties_regexes, source_lines);
				rename_common(RenamesMap3To4::csharp_signals_renames, reg_container.csharp_signal_regexes, source_lines);
				rename_csharp_functions(source_lines, reg_container);
				rename_csharp_attributes(source_lines, reg_container);
				custom_rename(source_lines, "public class ", "public partial class ");
			} else if (file_name.ends_with(".gdshader") || file_name.ends_with(".shader")) {
				rename_common(RenamesMap3To4::shaders_renames, reg_container.shaders_regexes, source_lines);
			} else if (file_name.ends_with("tres")) {
				rename_classes(source_lines, reg_container); 
				rename_common(RenamesMap3To4::shaders_renames, reg_container.shaders_regexes, source_lines);
				rename_common(RenamesMap3To4::builtin_types_renames, reg_container.builtin_types_regexes, source_lines);
				custom_rename(source_lines, "\\.shader", ".gdshader");
			} else if (file_name.ends_with("project.godot")) {
				rename_common(RenamesMap3To4::project_godot_renames, reg_container.project_godot_regexes, source_lines);
				rename_common(RenamesMap3To4::builtin_types_renames, reg_container.builtin_types_regexes, source_lines);
				rename_input_map_scancode(source_lines, reg_container);
				rename_joypad_buttons_and_axes(source_lines, reg_container);