Charset: Add missing return statement to _mb_ord().

This fixes a `return.missing` PHPStan error in `_mb_ord()`, fixing the only rule level 0 violation currently reported. In practice the `return` is in an unreachable code path, but static analysis may not be aware of this.

Developed in WordPress#12020.
Follow-up to r62424.

Props westonruter, dmsnell.
See #65342.


git-svn-id: https://develop.svn.wordpress.org/trunk@62436 602fd350-edb4-49c9-b593-d223f7449a82

Author: westonruter

src/wp-includes/compat.php

@@ -249,6 +249,8 @@ function _mb_ord( $string, $encoding = null ) {
 				( ( ord( $string[3] ) & 0x3F ) )
 			);
 	}
+
+	return false;
 }
 
 if ( ! function_exists( 'mb_substr' ) ) :