Merge branch '5.3' into 5.4

* 5.3:
  [GHA] fix running "Patch return types" step
  [Serializer] Don't pass null to preg_match()
  Use identity operator to prevent type juggling
  [Form] Don't trim unassigned unicode characters anymore

Author: nicolas-grekas

Tests/Util/StringUtilTest.php

@@ -16,11 +16,20 @@
 
 class StringUtilTest extends TestCase
 {
-    public function testTrim()
+    public function trimProvider()
     {
-        $data = ' Foo! ';
+        return [
+            [' Foo! ', 'Foo!'],
+            ["\u{1F92E}", "\u{1F92E}"], // unassigned character in PCRE versions of <PHP 7.3
+        ];
+    }
 
-        $this->assertEquals('Foo!', StringUtil::trim($data));
+    /**
+     * @dataProvider trimProvider
+     */
+    public function testTrim($data, $expectedData)
+    {
+        $this->assertSame($expectedData, StringUtil::trim($data));
     }
 
     /**

Util/StringUtil.php

@@ -31,7 +31,7 @@ private function __construct()
      */
     public static function trim(string $string)
     {
-        if (null !== $result = @preg_replace('/^[\pZ\pC]+|[\pZ\pC]+$/u', '', $string)) {
+        if (null !== $result = @preg_replace('/^[\pZ\p{Cc}\p{Cf}]+|[\pZ\p{Cc}\p{Cf}]+$/u', '', $string)) {
             return $result;
         }