Steps to reproduce:

 1. Enter fullscreen.  I use this function to do so:

    (defun emacs-max ()
      (interactive)
      (set-frame-parameter (selected-frame) 'fullscreen 'fullboth)
      (set-frame-parameter (selected-frame) 'vertical-scroll-bars nil)
      (set-frame-parameter (selected-frame) 'horizontal-scroll-bars nil))

 2. Create another frame with C-x 5 2.

 3. Delete that frame immediately with C-x 5 0.

 4. Emacs crashes. Crash report attached.