Handle the case of an ROI with only one POI.

[nbeaver]

This allows the POI manager to load an ROI file with a single POI.

Description

Add the ndmin argument to loadtxt to ensure the shape is correct even when there is only one POI to load. Previously the resulting shape for poi_names was () and for poi_coords was (3,), but with the fix it now has the correct shapes (1,) and (1, 3).

Motivation and Context

Currently, the POI manager will fail with an IndexError when attempting to load an ROI with a single ROI since loadtxt defaults to squeezing the dimensions.

How Has This Been Tested?

I have tested it manually by loading an ROI with a single POI.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] My code follows the code style of this project.
• [ ] I have documented my changes in the changelog (documentation/changelog.md)
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added/updated for the module the config example in the docstring of the class accordingly.
• [x] I have checked that the change does not contain obvious errors (syntax, indentation, mutable default values).
• [ ] I have tested my changes using 'Load all modules' on the default dummy configuration with my changes included.
• [ ] All changed Jupyter notebooks have been stripped of their output cells.

[timoML]

I can confirm the bug and the fix looks fine. @nbeaver Do you want to contribute this to qudi-iqo-modules as an PR as well? Alternatively, I can also push your fix there but this would drop your credit.