Update code that filters out IP addresses from the array of names. Instead of using mw.util.isIPAddress() to check if a name is an IP address, use a method that checks if a name is a temporary user name.
See code snippet below :
modules/ext.checkUser/checkuser/caMultiLock.js
if ( obj.name && obj.name === 'users[]' ) { // Only registered accounts (not IPs) can be locked if ( !mw.util.isIPAddress( obj.value ) ) { names.push( obj.value ); }