Error in `get_cross_corr_emissions_from_buff()` after switching days

[ubdbra001]

When moving from one day to the next an error is thrown when get_cross_corr_emissions_from_buff() is reached for the first time:

Exception has occurred: UnboundLocalError
local variable 'vel_glob_err' referenced before assignment

File "C:\Users\Daniel\Projects\PyCamPermanent\pycam\so2_camera_processor.py", line 2909, in get_cross_corr_emissions_from_buff
    res['flow_glob']._velo_eff_err.append(vel_glob_err)

https://github.com/twVolc/PyCamPermanent/blob/952b65ead4365f17a87bcbfc3864700a63098ba2/pycam/so2_camera_processor.py#L2867-L2901

cross_corr_buff only has a single data point from the previous day and so vel_glob and vel_glob_err are not retrieved and assigned (vel_glob = None by default, hence why the error is not thrown a line earlier)

[ubdbra001]

May be because:

• got_doas_fov is only set to True at the very start of processing and then reset set to False by reset_self() at end of each day. Which means get_emission_rate_from_buffer() is skipped in update_doas_calibration()
• first_image is not reset at the start of each day, not sure if this has a direct impact on the above error though.

Or could be a combination of the two.