minor #43778 Use try/finally to restore error handlers (derrabus)

This PR was merged into the 5.4 branch.

Discussion
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Use try/finally to restore error handlers

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | N/A
| License       | MIT
| Doc PR        | N/A

This PR attempts to make some code dealing with temporary error handlers a bit more robust by making sure the old error handler is always restored. A forgotten error handler is pretty hard to debug, so I'd like our code to be a it more defensive here.

Commits
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057716c6a2 Use try/finally to restore error handlers

Author: derrabus

Filesystem.php

@@ -737,15 +737,10 @@ private static function box(callable $func, ...$args)
         self::$lastError = null;
         set_error_handler(__CLASS__.'::handleError');
         try {
-            $result = $func(...$args);
+            return $func(...$args);
+        } finally {
             restore_error_handler();
-
-            return $result;
-        } catch (\Throwable $e) {
         }
-        restore_error_handler();
-
-        throw $e;
     }
 
     /**