System.Exception error on export

[Drakaic]

Tried to unpack a spritesheet and I received this error. No clue how to fix. I have cloned the source to github desktop and manually started the application from ASU.exe
System.Exception: An error occured whilst exporting frames.
---> System.ArgumentException: Parameter is not valid.

 at System.Drawing.Bitmap..ctor(Int32 width, Int32 height, PixelFormat format)   
 at ASU.UI.MainForm.ExportUnpackers(List`1 unpackers) in C:\Users\MCooper\Documents\GitHub\Alferd-Spritesheet-Unpacker\ASU\UI\MainForm.cs:line 1108   
 --- End of inner exception stack trace ---   

 at ASU.UI.MainForm.ExportUnpackers(List`1 unpackers) in C:\Users\MCooper\Documents\GitHub\Alferd-Spritesheet-Unpacker\ASU\UI\MainForm.cs:line 1222   
 at ASU.UI.MainForm.ExportButton_Click(Object sender, EventArgs e) in C:\Users\MCooper\Documents\GitHub\Alferd-Spritesheet-Unpacker\ASU\UI\MainForm.cs:line 1228