Ensure that no text properties leak to the overlay (Fix #533)

Author: minad

corfu.el

@@ -839,7 +839,7 @@ the last command must be listed in `corfu-continue-commands'."
     (overlay-put corfu--preview-ov 'priority 1000)
     (overlay-put corfu--preview-ov 'window (selected-window))
     (overlay-put corfu--preview-ov (if (= beg end) 'after-string 'display)
-                 (nth corfu--index corfu--candidates))))
+                 (substring-no-properties (nth corfu--index corfu--candidates)))))
 
 (defun corfu--preview-delete ()
   "Delete the preview overlay."