Load early-init.el if early-init-file is not bound *and* true

For Emacs 27, the symbol is still bound when using -Q, which means it
won't be loaded from bin/doom.

init.el

@@ -27,7 +27,7 @@
 ;;
 ;;; License: MIT
 
-(unless (boundp 'early-init-file)
+(unless (bound-and-true-p early-init-file)
   (load (concat (file-name-directory load-file-name) "early-init")
         nil t))