Fix segfault on no view history and :set autochpos

Could happen in vifmrc after starting vifm with `--no-configs`.

Thanks to ranousse.
Merge branch 'fix-autochpos-segfault'

Fix segmentation fault on no view history and ":set autochpos" in
vifmrc.

Could happen starting vifm with `--no-configs` option.

Fixes #44.

Thanks to ranousse.