Simplify code

Author: Seldaek

src/PHPStan/UnsafeStrictGroupsCallRule.php

@@ -57,7 +57,7 @@ public function processNode(Node $node, Scope $scope): array
             return [];
         }
 
-        $patternArg = $args[0] ?? null;
+        $patternArg = $args[0];
         if ($isPreg) {
             if (!isset($args[2])) { // no matches set, skip as the matches won't be used anyway
                 return [];
@@ -67,10 +67,6 @@ public function processNode(Node $node, Scope $scope): array
             $flagsArg = $args[2] ?? null;
         }
 
-        if ($patternArg === null) {
-            return [];
-        }
-
         $flagsType = PregMatchFlags::getType($flagsArg, $scope);
         if ($flagsType === null) {
             return [];