### 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_common(RenamesMap3To4::input_map_renames, reg_container.input_map_regexes, source_lines);
				custom_rename(source_lines, "config_version=4", "config_version=5");
			} else if (file_name.ends_with(".csproj")) {
				
			} else if (file_name.ends_with(".import")) {
				for (SourceLine &source_line : source_lines) {
					String &line = source_line.line;
					if (line.contains("nodes/root_type=\"Spatial\"")) {
						line = "nodes/root_type=\"Node3D\"";
					}
				}
			} else {
				ERR_PRINT(file_name + " is not supported!");
				continue;
			}
			for (SourceLine &source_line : source_lines) {
				if (source_line.is_comment) {
					continue;
				}
				String &line = source_line.line;
				if (uint64_t(line.length()) > maximum_line_length) {
					ignored_lines += 1;
				}
			}
		} else {
			reason.append(vformat("    ERROR: File has exceeded the maximum size allowed - %d KB", maximum_file_size / 1024));
			is_ignored = true;
		}
		uint64_t end_time = Time::get_singleton()->get_ticks_msec();
		if (is_ignored) {