Fixed trimming null raising TypeError; now returns empty string.

Author: Bilge

src/Strategy/Trim.php

@@ -7,6 +7,6 @@ class Trim extends Delegate
 {
     public function __invoke($data, $context = null)
     {
-        return trim(parent::__invoke($data, $context));
+        return trim((string)parent::__invoke($data, $context));
     }
 }

test/Integration/Mapper/Strategy/TrimTest.php

@@ -18,4 +18,14 @@ public function test(): void
 
         self::assertSame('foo', $trim([]));
     }
+
+    /**
+     * Tests that trimming null returns the empty string.
+     */
+    public function testNull(): void
+    {
+        $trim = (new Trim(null))->setMapper(new Mapper());
+
+        self::assertSame('', $trim([]));
+    }
 }