autocompletion triggered even on blank line

[jquelin]

1. create a document with the following content:

foobar bazzab frobnizer
#

2. set cursor position after the hash
3. type backspace

==> see autocompletion triggered, when it shouldn't (we're on a blank line!)

[waxhead]

Sewi, I think you worked on some of this didn't you?

[Sewi]

I think this is fixed, autocomp should not appear if there isn't \w before the cursor.