EQ bands bug: bands automatically getting enabled with certain behaviour

[Monospace-V]

Bug Summary

Adding the Equalizer (the native GUI one), enabling one band, then repeatedly hitting Ctrl-Z enables band after band.

Steps to reproduce

1. Add equalizer (LMMS) effect to instrument
2. Enable any band by clicking on it
3. Hit Ctrl-Z

Expected behavior

Band gets disabled / Ctrl-Z undoes last change

Actual behavior

Other bands get enabled

Screenshot

https://user-images.githubusercontent.com/76674645/126066039-6b871d62-24ed-4c9b-8022-eff1a31a6485.mp4 (video)

(I had enabled band 4, then hit Ctrl-Z twice)

Affected LMMS versions

1.2.0, 1.3 alpha, and presumably everything in between.

(Extra note: faced a bug where clicking one band would enable all bands. Is presumably related, but could not reproduce.)

[zonkmachine]

I think this could be a duplicate of #4898