Allow .ttt file as command line argument

[Andre Wichmann]

On JAC!'s computer, sometimes the tracker cannot open the source files in player/ on export. Evaluate and output the reason on error!

EDIT: Happens on double-click on a .ttt file (wrong working folder!)

[Pascal Leclerc]

Same thing happened to me when running TIATracker from command line, outside its directory. It works fine, but freezes on export because it doesn't find the player/ data. It should source all its files from the executable folder.