ERPparamGroup data handling

[mwprestonjr]

The way data is added, checked, and passed to the fit function in ERPparamGroup is buggy. has_data is set to True even if the time argument is not provided, leading to errors. Furthermore, time=None is passed to the fit function when fitting sequentially while time=self.time is passed when fitting in parallel leading to inconsistent behavior.

[mwprestonjr]

commit 17f47e7 partially fixed this issues. self.uncropped_time is now passed when fitting linearly or in parallel....

ERPparam.has_data() checks for both signal and time, while ERPparamGroup.has_data() only checks for signals . I will update these to have the same behavior