TypeError: trigger_error(): Argument #2 ($error_level) must be of type int, string given in trigger_error()

Problem/Motivation

Modules that use the getCountNewComments function (for example, Forum) give an error

TypeError: trigger_error(): Argument #2 ($error_level) must be of type int, string given in trigger_error()

Steps to reproduce

Install Forum (for example), navigate to default forum (general discussion). See WSOD.

Proposed resolution

Fix $error_level type from string to int