The deprecated null value for the method round has been changed to zero.

src/Extension/CoreExtension.php

@@ -581,6 +581,8 @@ function twig_replace_filter($str, $from)
  */
 function twig_round($value, $precision = 0, $method = 'common')
 {
+    $value = (float) $value;
+
     if ('common' === $method) {
         return round($value, $precision);
     }
@@ -589,8 +591,6 @@ function twig_round($value, $precision = 0, $method = 'common')
         throw new RuntimeError('The round filter only supports the "common", "ceil", and "floor" methods.');
     }
 
-    $value = (float) $value;
-
     return $method($value * 10 ** $precision) / 10 ** $precision;
 }
 

tests/Fixtures/filters/round.test

@@ -13,6 +13,8 @@
 
 {{ ''|round(-1, 'floor')}}
 {{ null|round(-1, 'floor')}}
+{{ null|round }}
+{{ null|round(2, 'ceil') }}
 --DATA--
 return []
 --EXPECT--
@@ -28,3 +30,5 @@ return []
 
 0
 0
+0
+0