[Stopwatch] Deprecate passing null in Section::get() method.

UPGRADE-4.4.md

@@ -108,6 +108,11 @@ Security
 
  * Implementations of `PasswordEncoderInterface` and `UserPasswordEncoderInterface` should add a new `needsRehash()` method
 
+Stopwatch
+---------
+
+ * Deprecated passing `null` as 1st (`$id`) argument of `Section::get()` method, pass a valid child section identifier instead.
+
 TwigBridge
 ----------
 

src/Symfony/Component/Stopwatch/CHANGELOG.md

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+4.4.0
+-----
+
+ * Deprecated passing `null` as 1st (`$id`) argument of `Section::get()` method, pass a valid child section identifier instead.
+
 3.4.0
 -----
 

src/Symfony/Component/Stopwatch/Section.php

@@ -62,6 +62,10 @@ class Section
      */
     public function get($id)
     {
+        if (null === $id) {
+            @trigger_error(sprintf('Passing null as 1st ("$id") argument of the "%s()" method is deprecated since Symfony 4.4, pass a valid child section identifier instead.', __METHOD__), E_USER_DEPRECATED);
+        }
+
         foreach ($this->children as $child) {
             if ($id === $child->getId()) {
                 return $child;