I'm trying to use the GRETNA toolbox to process some rs-fMRI data. But it is choking on the delete images step. I've used the default of 10 images and did not change any other settings. The MATLAB errors that I get are:

Undefined function 'fieldnames' for input arguments of type 'double'.

Error in psom_pipeline_init (line 305)
list_jobs = fieldnames(pipeline);

Error in psom_run_pipeline (line 379)
[tmp,flag_start] = psom_pipeline_init(pipeline,opt_init);

  Error in gretna_GUI_PreprocessInterface>RunEvent (line 2311)
psom_run_pipeline(pipeline,opt);

  Error in gretna_GUI_PreprocessInterface>RunButton_Callback (line 2431)
RunEvent(hObject , handles);

  Error in gui_mainfcn (line 96)
  feval(varargin{:});

  Error in gretna_GUI_PreprocessInterface (line 42)
  gui_mainfcn(gui_State, varargin{:});
 
Error in 
@(hObject,eventdata)gretna_GUI_PreprocessInterface('RunButton_Callback',hObject,eventdata,guidata(hObject))
 
  Error while evaluating uicontrol Callback

Any Ideas?