Fix various minor bugs found in merging

[JeanBilheux]

Error 1:

Traceback (most recent call last):
  File "/Volumes/G-DRIVE/git/ToFImaging/JupyterNotebooks/code/decorators.py", line 14, in wrapper
    function(self)
  File "/Volumes/G-DRIVE/git/ToFImaging/JupyterNotebooks/code/fit_interface.py", line 168, in prepare_data_button_clicked
    o_event.prepare_data()
  File "/Volumes/G-DRIVE/git/ToFImaging/JupyterNotebooks/code/prepare_data.py", line 65, in prepare_data
    o_norm = g(parent=self.parent)
NameError: name 'g' is not defined