Fix build

src/Monolog/Utils.php

@@ -249,7 +249,7 @@ final class Utils
         }
 
         $val = (int) $match['val'];
-        switch (strtolower($match['unit'] ?? '')) {
+        switch (strtolower($match['unit'])) {
             case 'g':
                 $val *= 1024;
             case 'm':