Fix a crasher when refreshing the list view with the default table.

Fix a crasher when refreshing the list view with the default table.

This crash will also happen when loading the list view with the default
table from a link or bookmark.

* src/main/java/org/glom/web/client/activity/DetailsActivity.java: Go
to the main document selection page when the document id hasn't been
set.
* src/main/java/org/glom/web/client/activity/ListActivity.java: Go to
the main document selection page when the document id hasn't been
set.
* src/main/java/org/glom/web/client/place/DetailsPlace.java: Use empty
values for the details place when the document id hasn't been set.
* src/main/java/org/glom/web/client/place/ListPlace.java: Use empty
values for the list place when the document id hasn't been set.