IndexOutOfRangeException in AsepriteFileLoader.LoadFile

[exokem]

Description

When calling AsepriteFileLoader.FromFile for a specific file, an IndexOutOfRangeException occurs. The exception occurs on line 373 in AsepriteFileLoader.cs when accessing the cel at index cels.Count in the frame targeted by a linked cel. I have been unable to determine what about this file causes the issue. The original file was very large (~3000 layers and ~60 frames) but the layer count at least does not seem to be related. I have pruned the original file to remove as much as possible while preserving the occurrence of the issue. The modified file has 7 layers and 14 frames and the issue persists.

Steps to Reproduce

The exception occurs when attempting to load a specific file.

To reproduce:

1. Download and extract the attached zip file (it should contain test_file_2.ase).
2. Call AsepriteFileLoader.FromFile using the path to the test file.

Alternatively, create a new file with this format:

Then attempt to load that file.
test_files.zip

Expected Behavior

The file should be loaded successfully and without error.

Actual Behavior

An exception occurs.

Exception has occurred: CLR/System.IndexOutOfRangeException
An unhandled exception of type 'System.IndexOutOfRangeException' occurred in System.Private.CoreLib.dll: 'Index was outside the bounds of the array.'
   at System.ThrowHelper.ThrowIndexOutOfRangeException()
   at System.ReadOnlySpan`1.get_Item(Int32 index)
   at AsepriteDotNet.IO.AsepriteFileLoader.LoadFile(String fileName, AsepriteBinaryReader reader, Boolean preMultiplyAlpha) in D:\Data\CS\AseExport\AsepriteDotNet\source\AsepriteDotNet\IO\AsepriteFileLoader.cs:line 373
   at AsepriteDotNet.IO.AsepriteFileLoader.FromStream(String fileName, Stream stream, Boolean leaveOpen, Boolean preMultiplyAlpha) in D:\Data\CS\AseExport\AsepriteDotNet\source\AsepriteDotNet\IO\AsepriteFileLoader.cs:line 55
   at AsepriteDotNet.IO.AsepriteFileLoader.FromFile(String path, Boolean preMultiplyAlpha) in 

Configuration

dotnet v8.0.100
The file has been saved with aseprite v1.3.6 and opens in aseprite without issue.
The issue occurs on windows x64, at least.

Other Information

No response

[exokem]

Just an extra note: I have a feeling this could just be a missing bounds check, but I don't know enough about the file format to know whether this is more likely to be a different problem. If I introduce a check for the index the file does appear to load correctly in that the exception does not occur, but again I don't know if this is actually enough.

[AristurtleDev]

Sorry for delay in response, taking a look at this now @exokem