Multiple DICOMs in same directory appear as a single image

[waltman]

Describe the bug
I have four 2D mammography images in the same directory. When I load them I only see a single image, and there's no way to see the others. After converting them to NiFTI, I can switch to the other images by clicking on them in the Images panel.

To Reproduce

1. Load CaPTk
2. Select File/Load/Image(s) from the menu, then navigate to a folder with multiple DICOMs
3. Select all of them and click the Open button
4. A single image appears in the panel below the Images panel
5. Click on any image in the Images panel. The image below doesn't change.
6. Convert the DICOMs to NiFTI by selecting Preprocessing/DICOM to NiFTI from the menu.
7. Repeat steps 2-5 in the NiFTI folder. Now the images DO change.

Expected behavior
The DICOM images should change just like the NiFTIs do.

Screenshots
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CaPTk Version v.1.9.0.Alpha
Desktop (please complete the following information):

• OS: Linux
• Version: Ubuntu 20.04.3 LTS

Additional context
Add any other context about the problem here.
It does seem to work when the DICOMs are in different directories.