Corrects #6110
BSD `seq` produces a down-counting sequence when the second argument is
smaller than the first, e.g.:
$ seq 2 1
2
1
$
While GNU `seq` produces no output at all:
$ seq 2 1
$
To accommodate for this behavior, only run `seq` when we are sure that
the second argument is greater than or equal to the first (in this case,
the second argument `line_count` should be greater than 1).
* Fix default Alt+W keybinding
The old keybinding would chop off the last line of the `whatis` output
when using a multi-line prompt. This fix corrects that.
* Make variable local and remove unneeded if statement
* Test that token is non-empty
