[TxMt] Option to allow cursor to be placed in the void

[Tim Harper]

I don't know what I did, or how I did it, but somehow TextMate places  
the cursor, by default, out in the void, where there are no tabs,  
spaces, or characters.

For example: I'm on line 1, column 80.  Line 2 has 5 characters.  I  
press down.  I'm on line 2, column 80.  I type the letter 'a'.  74  
spaces are inserted up to column 80, then the character 'a' is inserted.

How do I switch this behavior back, so that pressing down brings me to  
the end of the line, but not out in the void?

Thanks!
Tim