After upgrading from 1.5.1 to 1.5.2, Yakyak now has an extra visible native title bar in macOS Mojave:

Same issue present on 1.5.2 while running macOS Mojave Version 10.14.1 Beta (18B67a).

I have the same issue on Mojave and 1.5.2 installed this morning.
Same with 1.5.2 on High Sierra
I am also experiencing this on macOS Mojave.
I have a pr out for this, hopefully gets merged soon.
If you want to fix this on your local version, edit your main.js file on line 206. Change 'hidden-inset' to 'hiddenInset'.
New line will look like this:
titleBarStyle: process.platform === 'darwin' ? 'hiddenInset' : void 0,
Should fix it until a new release is rolled out.
Most helpful comment
I have a pr out for this, hopefully gets merged soon.
If you want to fix this on your local version, edit your
main.jsfile on line 206. Change 'hidden-inset' to 'hiddenInset'.New line will look like this:
Should fix it until a new release is rolled out.