If the URL is not meant to exist, as you say, and Google can’t find it (confirming it doesn’t exist) then I don’t think you have a problem. Someone, somewhere, has a malformed link to your site, and there’s not a lot you can do about it. If it bothers you, I believe there’s an option in GWT to tell Google to ignore a particular URL, but whether you can tell it to ignore a non-existent URL, I don’t know.
If you suddenly started getting a lot of these reports for a whole host of non-existent links, that might be a cause for concern, but one? I don’t think so.
Yes i have a sitemap,cant find any error there.These 185 URL’s i get from GWT crawl error as Not Found errors.Google is crawling my website but crawlers find difficulty in crawling if site has alot of 404 errors.