Fixed `presentation-history-previous' to work properly with an empty history.
Fixed `presentation-history-previous' to work properly with an empty
history.

antifuchs/mcclim,swflint/McCLIM,onixie/mcclim,onixie/mcclim,slyrus/mcclim,slyrus/mcclim,onixie/mcclim,antifuchs/mcclim,swflint/McCLIM,swflint/McCLIM