Actual behavior:
Windows/Preferences/Xnat Conenction offers several text fields for connection settings to start an XNAT session.
Leaving the text fields empty and clicking 'OK' throws a 'Saving preferences failed' error, stating 'The connection parameters in XNAT Preferences were empty. [...]'.

This also happens if the user clicks on the Xnat Connection preferences pages (accidentally) but does not want to use XNAT / start an XNAT session. If the user then clicks on another preference page, e.g. Segmentation, changes some settings and clicks 'OK', the 'Saving preferences failed' error from the Xnat Connection preference page still pops up.

Expected behavior:
Clicking ''OK' should accept the settings made in several preference pages. Checking whether the Connection parameters can be used to start an XNAT session should be done at another place, e.g. the 'TestConnection()'-function.