Fix back button popstate not working on the first pushState

[fritx]

Apperance:
The back button does not work right after the first link navigation, but begins to work after the second navigation.
( Tried Chrome 120.0.6099.129 and Safari 16.6 (17615.3.12.11.3, 17615) )

Reason:
The first popstate e.state=null, and getting path=undefined

Steps to reproduce:

cd simple-blog
# both
nue
# and
nue build --production
nue serve --production

Fix Approach:
Record the initial_path and use it when path is undefined.

Or maybe, just loadPage(location.pathname), regardless of e.state.path ? ref: https://github.com/fritx/silent/blob/2x/blog/vendor/blog.js#L409-L413

ref: window.onpopstate, event.state == null?
https://stackoverflow.com/questions/11092736/window-onpopstate-event-state-null

[tipiirai]

Thank you @fritx. These fixes are great!

[tanwwg]

I don't think it's fixed yet, I get null null whenever I hit the back button on 0.3.3.

[fritx]

Still: window.onpopstate, event.state == null?
https://stackoverflow.com/questions/11092736/window-onpopstate-event-state-null

Looks like calling history.pushState(initialState) twice is more reliable. Thoughts? cc @nobkd
I'm not sure as I tried it only once and it worked fine on my side.