Stack Images - input stays inactive after SI is closed

[davidh]

1. start Stack Images
2. load an image into the dialog
3. close the dialog using the x button -> the input image remains inactive (it should probably get focus)

Now if you run some of the other transformations the changes made to the input will not show in the image area preview.

The preview is refreshed only by toggling the dialog preview buttons.

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one more observation:

start Stack Images
do nothing
close the dialog -> there remains a black square in the image areauntil you click the input

[jsachs]

I didn't quite fix this last time, but it should now be fixed for the next release.