fix: Corrects copying options from existing notification for boolean values

[melopilosyan]

First of all, nice plugin. And the replace existing feature makes it even better. I enjoyed integrating it into rspec-integrated.nvim.

So. To reproduce the bug, execute this snippet on the master.

local prev = require("notify")("Won't show up in history", "INFO", {
  title =  "Note",
  hide_from_history = true,
})
require("notify")("Should show up, but doesn't", nil, {
  replace = prev,
  hide_from_history = false,
})

Then run the :Notifications command and notice the empty history. Although the second one is told not to hide.