Fixed typo: "souce" to "source"
Don't try to return boundary changes for places with no MapIt area

We were getting error emails for a couple of places that had no MapIt
area associated with them - these are historic data where it's going to
be difficult to get missing data, so let's just settle for not showing
boundary changes for these cases.

Fixes #1335 and #1377.
Merge branch 'fix-for-missing-mapit-areas'
Add ability to view all Hansard appearances for a person.

Closes #1405