EQ in a macro fails when applied to files

[petersampsonaudacity]

Bug description

When either EQ effect is used in a macro fails with an error message when applied to files - it works fine if you apply it to audio in a project.

This is a regression on 3.3.3 where the simple macro runs on files with no error message.

Steps to reproduce

1. create a simple Macro with Filter Curve EQ in it (or Graphic EQ)
2. Apply it to files
3. Observe error message

I tested further and added an Export to WAV command and no files or macro-output folder were created.

Expected behavior

This macro should work with no error message

Actual behavior

Step 1

Step 3

Audacity Version

3.4.1 and 3.4.2 latest Beta (in fact all 3.4.x)

Operating system

Windows 10 - but assume all OS

Additional context

Originally reported by a Forum user:
New bug in 3.4.1. Had to revert to 3.4.0
https://forum.audacityteam.org/t/new-bug-in-3-4-1-had-to-revert-to-3-4-0/89756

[dozzzzer]

Bisects to 618d61e

[saintmatthieu]

Bisects to 618d61e

Thanks @dozzzzer ; but that means it's already present in 3.4.0, which contradicts that forum user which @petersampsonaudacity reported he said "New bug in 3.4.1. Had to revert to 3.4.0"

Anyway, I think I can at least provide a fix for this github issue's very description.

[chinakov]

Tested. Thank you!