Going into Options > Addons > AddOnSkins the resulting panel is blank.

It seems the calculation of an argument is failing for the following line:
AS.Options.args.embed.args.DualEmbedSystem.args.EmbedLeftWidth = ACH:Range(L['Window One Width'], nil, 3, { min = function() return max(floor((ES.Main:GetWidth() or 0) * .25), 100) end, max = function() return max(floor((ES.Main:GetWidth() or 0) * .75), 300) end, step = 1 }, nil, nil, nil, function() return not AS:CheckOption('EmbedSystemDual') end)
Specifically this part:
{ min = function() return max(floor((ES.Main:GetWidth() or 0) * .25), 100) end, max = function() return max(floor((ES.Main:GetWidth() or 0) * .75), 300) end, step = 1 }

I cannot imagine this being the right way to fix it, but as a workaround replacing that entire part with nil will result in the menu being accessible again.

Closing as this was resolved with the latest update