Selection widgets have the possibility to be optional. In that case a "cross" is used to remove the current selection.
If there are multiple fitting / matching nodes for the selection widget, another node is select which does not allow to have NO selection using the "cross".
That probably only happens with the auto-selection mode on because I can identify two different cases:

1. open the MITK workbench, open the Properties view
2. load two images and select one in the selection widget of the Properties view
3. remove the selection using the cross
4. no node is selected and an info text is printed

1. open the MITK workbench, open the Measurement view
2. load two images and select one in the selection widget of the Measurement view
3. remove the selection using the cross
4. the second node is selected
5. remove the selection using the cross
6. the first node is selected again

This also happens e.g. with the Image Cropper view