That console error is not related. But you can delete folder ~/Library/Caches/com.edgenius.osx.TextNut (or move it to somewhere) as its file permission looks invalid and it maybe cause TextNut cannot restore to normal state.
One possible reason, that pure editor window is only open when you have used "open by" from Finder and TextNut exited unexpected. When restart TextNut, it try to restore original window - so it open main window and that editor window. But the weird thing is, after your close that pure editor window, and exit normally, at next restart, TextNut supposes to open normal main window.
Can you check this option in System -> General - "Close window when quitting an app"?
If TextNut working normal, you can restore that option again. The worse, you may have to restart the OS and try again.