zynaddsubfx gui crashes

Bug Summary the zynadsubfx GUI opens to general settings but crashes when you press the "show GUI" button

Steps to reproduce lmms 1.2.2 open new project and add the zynadsubfx plugin. then click on its pane to open general settings. when you then open the GUI, the general settings will close and any note(s) that are in that Channel will not play until you restart lmms

Expected behavior

GUI opens

Actual behavior

GUI crashes and channel is silent until lmms is restarted
Edit: Demo project from screenshot, Hyper X - You [Future Bass].mmpz

Screenshot

see attached screenshot, (just using someone's music I found on the sharing platform)
Hyper X - You [Future Bass]_ - LMMS 1.2.2 - [Song-Editor] 2020-11-14 10-12-08.zip

Affected LMMS versions 1.2.2 normal version

I would love to help the lmms team but unfortunately, I cannot code but if there is anything else I could do I would be happy to help.

Reproduce the crash in LMMS 1.2.2 by opening a new project, adding the zynaddsubfx plugin, and pressing the plugin pane's "show GUI" button; the linked demo project may help. Confirm whether the GUI closes or crashes and whether the channel becomes silent, then identify the relevant LMMS plugin or GUI code and add a regression test if the project supports one.