bug symfony#48823 [Cache] Fix possibly null value passed to preg_match() in RedisTrait (chalasr)

This PR was merged into the 5.4 branch.

Discussion
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[Cache] Fix possibly null value passed to preg_match() in RedisTrait

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -
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Commits
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89e6c2f [Cache] Fix possibly null value passed to preg_match() in RedisTrait

Author: chalasr

src/Symfony/Component/Cache/Traits/RedisTrait.php

@@ -237,7 +237,7 @@ public static function createConnection(string $dsn, array $options = [])
                         restore_error_handler();
                     }
                     if (!$isConnected) {
-                        $error = preg_match('/^Redis::p?connect\(\): (.*)/', $error, $error) ? sprintf(' (%s)', $error[1]) : '';
+                        $error = preg_match('/^Redis::p?connect\(\): (.*)/', $error ?? '', $error) ? sprintf(' (%s)', $error[1]) : '';
                         throw new InvalidArgumentException(sprintf('Redis connection "%s" failed: ', $dsn).$error.'.');
                     }