checkbox-touch: fix popup not showing when resume failed

This patch fixes error popup not being shown when exception was caught when
trying to resume session

Signed-off-by: Maciej Kisielewski <maciej.kisielewski@canonical.com>
"automatic merge of lp:~kissiel/checkbox/cbt-fixes/ by tarmac [r=sylvain-pineau][bug=][author=kissiel]"