Make more anonymous functions static

Author: oliverklee

src/CSSList/CSSList.php

@@ -413,7 +413,7 @@ protected function renderListContents(OutputFormat $oOutputFormat)
             $oNextLevel = $oOutputFormat->nextLevel();
         }
         foreach ($this->aContents as $oContent) {
-            $sRendered = $oOutputFormat->safely(function () use ($oNextLevel, $oContent): string {
+            $sRendered = $oOutputFormat->safely(static function () use ($oNextLevel, $oContent): string {
                 return $oContent->render($oNextLevel);
             });
             if ($sRendered === null) {

src/RuleSet/RuleSet.php

@@ -266,7 +266,7 @@ protected function renderRules(OutputFormat $oOutputFormat)
         $oNextLevel = $oOutputFormat->nextLevel();
         foreach ($this->aRules as $aRules) {
             foreach ($aRules as $rule) {
-                $sRendered = $oNextLevel->safely(function () use ($rule, $oNextLevel): string {
+                $sRendered = $oNextLevel->safely(static function () use ($rule, $oNextLevel): string {
                     return $rule->render($oNextLevel);
                 });
                 if ($sRendered === null) {