Warning (2) : Attempt to read property "id" on null [in /home/civicdata/public_html/src/Controller/BlogsController.php, line 139]
Warning (512) : Unable to emit headers. Headers sent in file=/home/civicdata/public_html/vendor/cakephp/cakephp/src/Error/Renderer/HtmlErrorRenderer.php line=37 [in /home/civicdata/public_html/vendor/cakephp/cakephp/src/Http/ResponseEmitter.php, line 65]
Warning (2) : Cannot modify header information - headers already sent by (output started at /home/civicdata/public_html/vendor/cakephp/cakephp/src/Error/Renderer/HtmlErrorRenderer.php:37) [in /home/civicdata/public_html/vendor/cakephp/cakephp/src/Http/ResponseEmitter.php, line 158]
Warning (2) : Cannot modify header information - headers already sent by (output started at /home/civicdata/public_html/vendor/cakephp/cakephp/src/Error/Renderer/HtmlErrorRenderer.php:37) [in /home/civicdata/public_html/vendor/cakephp/cakephp/src/Http/ResponseEmitter.php, line 191]
Error: Expression `Blogs.blog_category_id` has invalid `null` value. If `null` is a valid value, operator (IS, IS NOT) is missing.

Expression `Blogs.blog_category_id` has invalid `null` value. If `null` is a valid value, operator (IS, IS NOT) is missing. 📋

InvalidArgumentException
CORE/src/Database/Expression/QueryExpression.php at line 747 (edit)
            $operator = '!=';
        }
        if ($value === null && $this->_conjunction !== ',') {
            throw new InvalidArgumentException(
                sprintf(
                    'Expression `%s` has invalid `null` value.'
                    . ' If `null` is a valid value, operator (IS, IS NOT) is missing.',
                    $expression,

If you want to customize this error message, create templates/Error/error500.php