* lisp/isearch.el: Fix corner cases of isearch-lazy-count.
* lisp/isearch.el (isearch-mode): Reset isearch-lazy-count-current and isearch-lazy-count-total to nil, so when isearch-mode is started, there should be no counts from previous Isearch. (isearch-lazy-highlight-new-loop): Call isearch-message after resetting lazy-count variables only when isearch-mode is started. This avoids the problem of inappropriate calls of isearch-message-function when query-replace in the minibuffer performs lazy-highlighting that used to call minibuffer-history-isearch-message unnecessarily.