Catchable fatal error: Object of class WP_Error could not be converted to string

Try downloading WordPress again and delete then replace your copies of everything except the wp-config.php file and the /wp-content/ directory with fresh copies from the download. This will effectively replace all of your core files without damaging your content and settings. Some uploaders tend to be unreliable when overwriting files, so don’t forget to delete the original files before replacing them.

James Huff @
I did the same you suggested but the resolve is same. Check the screenshot

https://i59.tinypic.com/etv6h2.jpg

There was an issue with comments table and I repaired it. It worked fine then.

Problem Resolved

Thanks for sharing your solution.