allow empty shot for single shot call

matlab/gdat.m

@@ -188,7 +188,7 @@ try
     args = [{shot,data_request},varargin_eff];
   end
   % treat multiple shot numbers
-  if nargin > 0 && isnumeric(shot) && ~isempty(shot)
+  if nargin > 0 && isnumeric(shot)
     args_in = args;
     if ~isempty(shot)
       for i=1:numel(shot)