Reevaluate erroneous current result in history

Bug: 33555997

We were losing the error message by never evaluating for
HISTORY_MAIN_INDEX. But in the error case, we need to regenerate the
error notification.

We now store a special error value in the result string, so that
we can distinguish the error case.

Change-Id: I1311ce94a214da01d2e975666f6cb927fcd836f1