ImageJ2 Options dialog can be opened more than once

The dialog found under "Edit -> Options -> ImageJ2..." is not modal and can be opened multiple times. The option "Use SCIFIO when opening files (BETA!)" can be simultaneously checked and unchecked across the resulting instances.

Start from the Edit -> Options -> ImageJ2... menu entry and trace how the options dialog is opened. Reproduce the issue by opening multiple instances and toggling "Use SCIFIO when opening files (BETA!)". Done means the dialog cannot be opened more than once and the option has one consistent state.

Written by the indexing model from the issue text.