How to reproduce:
1. Open attached "case_1275324.zip" project
2. Make sure that the Memory Profiler package is installed
3. Enter the Play mode
4. Open Window/Analysis/Memory Profiler window
5. In the File Explorer, open the case_1275324/MemoryCaptures folder
6. Rename "Test.png" file to "1Test.png" file
7. In the Unity editor, Select the Memory Profiler window and observe the black image
8. Switch back to the MemoryCaptures folder
9. Rename "1Test.png" file back to "Test.png" file
10. In the Unity editor, select the Memory Profiler window and observe the black image

Expected result: The image preview in the Memory Profiler window is updated and visible
Actual result: The image preview in the Memory Profiler is not updated and is black

Reproducible with: 2019.4.10f1, 2020.1.5f1, 2020.2.0b2 (Memory Profiler 0.2.4-preview.1, 0.2.5-preview.1)
Could not test with: 2018.4.27f1 (png file is not created when capturing)

Notes: The image in the Memory Profiler window is updated after restarting the Memory Profiler