Handle images arriving simultaneously and images being deleted in Live Viewer (Intensity Plot)

[MikeSullivan7]

Summary

When the Live Viewer image display can handle cases where images arrive together quickly or when images are deleted/renamed etc, this behaviour needs to be reflected when the intensity plot is updated or when the ROI is moved.

Steps To Reproduce

Open the Live Viewer
With images showing and the Intensity plot active. delete images in the directory. The image should update in the LV but the mean is not recalculated correctly

Current Behaviour

When the overall state of the images in the directory changes, the Intensity plot does not update and instead attempts to add further data (the latest image) which is not correct

Expected Behaviour

When the overall state of the images in the directory changes, the Intensity plot should update appropriately by clearing and replotting.