Stale browser state allows bypass of Exported state edit prohibition

User story:
When correcting a statement, edits are made then set to NPO Approved to transition to Exported. However, export trigger is in admin panel (which opens in a new tab). This leaves the last statement edited potentially in a vulnerable position - it's still in NPO approved in it's tab; even though it's actually exported -which prohibits editing.

To Reproduce:
1. select a statement in NPO approved state.
2. click admin panel
3. navigate to the new tab (admin panel)
4. in admin panel, select Create New Export
5. navigate to original composer tab (statement visible in front-end)
6. make an edit.
7. **notice you are permitted to do so.**
8. Composer then saves that change, and refreshes.
9. upon refresh, the statement is set to Exported, and further edits are not allowed.