Prior unit cell option isn't honoured for "index one frame"
Steps to reproduce:
- Load some data
- Click "Index this frame"
- Unselect "Automatically choose the indexing methods"
- Set a unit cell
- Deselect all methods except for asdf
- Deselect "Prior unit cell" for that method
- Click Run
- Observe that the log region says that asdf-nolatt-cell was used
- Click "Index this frame"
- Expand the list of indexing methods
- Observe that "Prior unit cell" is selected again for asdf
Expected result: At step 8: Log region should say "asdf-nolatt-nocell" At step 11: Prior unit cell should still be deselected