GTK Scale/Volume Buttons Show Muted Icon on Startup

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On Thursday, 25 April 2019 at 11:36:26 UTC, Ron Tarrant wrote:
> When running this example of a VolumeButton, ...

When using `setValue(initialValue)` after `setAdjustment()` the 
scale seems have the correct value. If in addition the Adjustment 
is created with an initial value different from the 
`initialValue` used with `setValue()` then the icons are also 
correct on startup. Though I don't know why that is. The loading 
issue doesn't happen here (on linux).