I stumbled upon a strange bug.

1. Open a new window with Cmd-N

2. Paste some text into the window.   Note that the tab does not show that the document has unsaved changes.  You can now type text and make other edits.  The document never detects that there are unsaved changes.   If you press Cmd-W the window will close without asking to save.

This does not happen if you first type some text after opening the window and then do the paste.

TextMate version 2.0-beta.12.15

OSX version 10.11.6