System Exception if there is whitespace in the export path.

[BuddhaRandom]

After copying and pasting path, i.e. C:\Project\etc\ there was a System Exception. Removing the trailing whitespace fixes the issue.

`System.Exception: An error occured whilst exporting frames.
---> System.Runtime.InteropServices.ExternalException: A generic error occurred in GDI+.

 at System.Drawing.Image.Save(String filename, ImageCodecInfo encoder, EncoderParameters encoderParams)   
 at ASU.UI.MainForm.ExportUnpackers(List`1 unpackers) in C:\Users\MCooper\Documents\GitHub\Alferd-Spritesheet-Unpacker\ASU\UI\MainForm.cs:line 1136   
 --- 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`