GTK bug on Mac

[ndbroadbent]

Hello, thanks for this awesome tool! I've been working with a lot of PDFs, so this has been incredibly useful.

I've been experiencing a UI bug that makes it difficult to read the text on the bottom right:

Do you know what might be causing that?

Don't know if this is related, but I'm also getting these warnings in the console:

Gdk-WARNING **: Unsupported source GdkWindow
	from /Users/ndbroadbent/.rvm/gems/ruby-2.4.2/gems/ruby-gtkhex-0.2.0/lib/gtkhex.rb:359:in `block in initialize'
	from /Users/ndbroadbent/.rvm/gems/ruby-2.4.2/gems/pdfwalker-1.0.0/lib/pdfwalker/walker.rb:52:in `main'
	from /Users/ndbroadbent/.rvm/gems/ruby-2.4.2/gems/pdfwalker-1.0.0/lib/pdfwalker/walker.rb:52:in `start'
	from /Users/ndbroadbent/.rvm/gems/ruby-2.4.2/gems/pdfwalker-1.0.0/bin/pdfwalker:30:in `<top (required)>'