avy.el (avy-goto-char-timer): Obey avy-background for initial search

Fixes #259

avy.el

@@ -1911,6 +1911,8 @@ Otherwise, the whole regex is highlighted."
   (let ((str "")
         (re-builder (or re-builder #'regexp-quote))
         char break overlays regex)
+    (unwind-protect
+         (progn
            (avy--make-backgrounds
             (avy-window-list))
            (while (and (not break)
@@ -1972,7 +1974,8 @@ Otherwise, the whole regex is highlighted."
                                (cons (cons (overlay-start ov)
                                            (overlay-end ov))
                                      (overlay-get ov 'window)))
-                             overlays)))
+                             overlays)))
+      (dolist (ov overlays)
         (delete-overlay ov))
       (avy--done))))