Empty/initialize fields

[XX-Yin]

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Describe changes:

Clear/initialize some fields when starting a new session.

What issues or discussions does this update address?

To clear or initialize certain fields from previous sessions when the new session is started without restarting the GUI. These fields may interfere with the generation of the manifest file if not reset.

Describe the expected change in behavior from the perspective of the experimenter

No

Describe any manual update steps for task computers

No

Was this update tested in 446/447?

Tested on 323_Ephys3

[alexpiet]

@micahwoodard Can you please review this?

[micahwoodard]

I don't quite know the downstream effect but would these variables be better initialized as None? seems weird to me that they are just empty stings but maybe that is what the code is expecting downstream

[micahwoodard]

Also does this fix #1124?

[micahwoodard]

Why are we deleting this one and not clearing it like the others?

[micahwoodard]

Same question here