server/template.Defer: panic: html/template: cannot Clone "" after it has executed

[bep]

I thought I had fixed this, but working on a new JS feature I'm using template.Defer extensively and get the error above on some rebuilds. Note that this is not an issue for regular builds.

[bep]

OK; I think I finally understand how this happens, which is a great start:

1. Start server in fast render mode (default) and load home page. Edit baseof.html template, home rebuilds OK.
2. Navigate to some other page that uses that same baseof.html template ... boom.

Note that since we fixed the issue with "stuck server errors", this issue isn't as painful as it was, as one more edit will get you out of the error state.