Sencha Themer "Cannot read property 'isUniversal' of null

Sencha Themer v1.3.9.197 Running on Mac

I get this error trying to open a theme:

TypeError: Cannot read property 'isUniversal' of null
    at themes.concat.filter.t (/Applications/Sencha/Themer/Sencha Themer.app/Contents/Resources/app.asar/themer/lib/sencha-json/Workspace.js:150:60)
    at Array.filter (native)
    at NpmWorkspace._findTheme (/Applications/Sencha/Themer/Sencha Themer.app/Contents/Resources/app.asar/themer/lib/sencha-json/Workspace.js:150:47)
    at Theme.getBaseTheme (/Applications/Sencha/Themer/Sencha Themer.app/Contents/Resources/app.asar/themer/lib/sencha-json/Package.js:120:51)
    at Theme.get baseTheme [as baseTheme] (/Applications/Sencha/Themer/Sencha Themer.app/Contents/Resources/app.asar/themer/lib/sencha-json/Package.js:84:46)
    at Theme._ensureDefaultsInSassPath (/Applications/Sencha/Themer/Sencha Themer.app/Contents/Resources/app.asar/themer/lib/Theme.js:263:35)
    at Theme.migrate (/Applications/Sencha/Themer/Sencha Themer.app/Contents/Resources/app.asar/themer/lib/Theme.js:99:14)
    at Promise (/Applications/Sencha/Themer/Sencha Themer.app/Contents/Resources/app.asar/themer/lib/ThemeUtil.js:280:19)
    at ThemeUtil.openTheme (/Applications/Sencha/Themer/Sencha Themer.app/Contents/Resources/app.asar/themer/lib/ThemeUtil.js:274:16)
    at callFunction (/Applications/Sencha/Themer/Sencha Themer.app/Contents/Resources/electron.asar/browser/rpc-server.js:251:18)