Added a better error message for when the user forgets to add a subject list in the main window when running group-level analysis (newly necessary for correctly parsing unique subject IDs for repeated measures).
Added a better error message for when the user forgets to add a subject list in the main window when running group-level analysis (newly necessary for correctly parsing unique subject IDs for repeated measures).

danlurie/C-PAC,danlurie/C-PAC,roijo/C-PAC_complexitytools,roijo/C-PAC_complexitytools,roijo/C-PAC_complexitytools,danlurie/C-PAC,roijo/C-PAC_complexitytools,danlurie/C-PAC