LV2 Calf plugins UI and file loading

[DHMike57]

Describe the bug

• Calf fluidsynth show ui button only opens and closes the calf ui once, then fails to respond. Closing the window yields (element:965421): GLib-CRITICAL **: 09:37:32.760: Source ID 239 was not found when attempting to remove it in the console
• Attempting to load a soundfont fails (and is not remembered on subsequent attempts).
• Other calf plugins appear to have a similar problem with the 'show ui' button,

To Reproduce Steps to reproduce the behavior:

• Load calf fluidsynth
• click 'show ui' (ui appears)
• load soundfont through plugin menu (fails)
• click 'hide ui' (ui closes)
• click 'show ui' (no response)

Desktop (please complete the following information):

• OS: arch linux
• Version : up to date

Standalone or Plugin

• standalone current git