fix(thread-list): Prevent empty state from showing when loading list
fix(thread-list): Prevent empty state from showing when loading list

- EmptyState should only be displayed when the thread-list is actually
empty, not while it is being loaded
- Update ObservableListDataSource to have a state of loaded only when
the requested range is > 0, i.e. when we are actually requesting threads

simonft/nylas-mail,nirmit/nylas-mail,nirmit/nylas-mail,nirmit/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail,nylas/nylas-mail,nylas/nylas-mail,nylas/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,nylas/nylas-mail