Currently lusty-explorer unconditionally splits the lowest window on the frame. But split-window can fail for a multitude of reasons, many of which are associated with the geometry or flags of the currently-open window. So on failure, delete the current window and retry the split (failing hard if that still fails). (We must delete the current window in this case, since otherwise lusty-buffer-explorer will get very confused about which window we are trying to change the current buffer of. Always creating a new window also means we can ignore complexities introduced by things like dedicated windows.)
This makes it possible to have different setups for file and buffer completion. For example, I bind backward-kill-word to DEL for file completion, but for buffer completion I don't like that.
Thanks to Tassilo Horn.
Improves compability with ECB, and perhaps other packages.