An attachment cannot be viewed the first time it is clicked

In order to view the attachments of a feature (or their thumbnails), it's currently necessary to:

1. identify the feature
2. view its list of attachments
3. tap to individually request viewing at least one attachment
4. exit the view to return to the map
5. identify another feature or otherwise deselect the current feature
6. re-select the same feature from step 1 and again commence with step 2

Observations:
- thumbnails will be created
- attachments themselves will be viewable

Start by tracing the iOS attachment and feature-selection flow described in the issue, including thumbnail creation and attachment viewing. Reproduce the first-click behavior, then verify that attachments and thumbnails are viewable without deselecting and reselecting the feature.

Written by the indexing model from the issue text.