bug #9416 fixed issue with clone now the children of the original form are preserved and the clone form is given new children (yjv)

This PR was merged into the 2.3 branch.

Discussion
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fixed issue with clone now the children of the original form are preserved and the clone form is given new children

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 9414
| License       | MIT
| Doc PR        |
this commit fixes #9414

Commits
-------

b952bcb fixed issue with clone now the children of the original form are preserved and the clone form is given new children

Author: fabpot

Form.php

@@ -170,6 +170,8 @@ public function __construct(FormConfigInterface $config)
 
     public function __clone()
     {
+        $this->children = clone $this->children;
+        
         foreach ($this->children as $key => $child) {
             $this->children[$key] = clone $child;
         }

Tests/CompoundFormTest.php

@@ -141,6 +141,7 @@ public function testCloneChildren()
 
         $this->assertNotSame($this->form, $clone);
         $this->assertNotSame($child, $clone['child']);
+        $this->assertNotSame($this->form['child'], $clone['child']);
     }
 
     public function testNotEmptyIfChildNotEmpty()