fix(config): add null coalescing fallback in getValueBool before strtolower

Followup to #59646: guard against null reaching strtolower() in both
AppConfig and UserConfig getValueBool(). Also aligns AppConfig with the
(string) cast added in UserConfig by the original PR.

Signed-off-by: skjnldsv <skjnldsv@protonmail.com>

Author: skjnldsv

build/psalm-baseline.xml

@@ -3478,11 +3478,6 @@
       <code><![CDATA[$CONFIG]]></code>
     </UndefinedVariable>
   </file>
-  <file src="lib/private/Config/UserConfig.php">
-    <RedundantCast>
-      <code><![CDATA[(string)$this->getTypedValue($userId, $app, $key, $default ? 'true' : 'false', $lazy, ValueType::BOOL)]]></code>
-    </RedundantCast>
-  </file>
   <file src="lib/private/Console/Application.php">
     <NoInterfaceProperties>
       <code><![CDATA[$this->request->server]]></code>

lib/private/AppConfig.php

@@ -424,7 +424,15 @@ public function getValueFloat(string $app, string $key, float $default = 0, bool
 	 * @see IAppConfig for explanation about lazy loading
 	 */
 	public function getValueBool(string $app, string $key, bool $default = false, bool $lazy = false): bool {
-		$b = strtolower($this->getTypedValue($app, $key, $default ? 'true' : 'false', $lazy, self::VALUE_BOOL));
+		// The explicit (string) cast and ?? null guard defend against a PHP OPcache bug where
+		// values passed by reference across function boundaries can have their type corrupted
+		// (e.g. bool returned as int, or null). Affects PHP 8.x with OPcache enabled; fixed
+		// upstream in https://github.com/php/php-src/pull/21973. Keep until minimum PHP version
+		// is bumped. Psalm sees the declared return type (string) and flags these as redundant.
+		/** @psalm-suppress RedundantCondition, TypeDoesNotContainNull */
+		$value = $this->getTypedValue($app, $key, $default ? 'true' : 'false', $lazy, self::VALUE_BOOL) ?? ($default ? 'true' : 'false');
+		/** @psalm-suppress RedundantCast */
+		$b = strtolower((string)$value);
 		return in_array($b, ['1', 'true', 'yes', 'on']);
 	}
 

lib/private/Config/UserConfig.php

@@ -682,11 +682,15 @@ public function getValueBool(
 		bool $default = false,
 		bool $lazy = false,
 	): bool {
-		// The explicit (string) cast guards against a PHP OPcache bug where values passed
-		// by reference across function boundaries can have their type corrupted (e.g. bool
-		// returned as int). Affects PHP 8.x with OPcache enabled; fixed upstream in
-		// https://github.com/php/php-src/pull/21973. Keep until minimum PHP version is bumped.
-		$b = strtolower((string)$this->getTypedValue($userId, $app, $key, $default ? 'true' : 'false', $lazy, ValueType::BOOL));
+		// The explicit (string) cast and ?? null guard defend against a PHP OPcache bug where
+		// values passed by reference across function boundaries can have their type corrupted
+		// (e.g. bool returned as int, or null). Affects PHP 8.x with OPcache enabled; fixed
+		// upstream in https://github.com/php/php-src/pull/21973. Keep until minimum PHP version
+		// is bumped. Psalm sees the declared return type (string) and flags these as redundant.
+		/** @psalm-suppress RedundantCondition, TypeDoesNotContainNull */
+		$value = $this->getTypedValue($userId, $app, $key, $default ? 'true' : 'false', $lazy, ValueType::BOOL) ?? ($default ? 'true' : 'false');
+		/** @psalm-suppress RedundantCast */
+		$b = strtolower((string)$value);
 		return in_array($b, ['1', 'true', 'yes', 'on']);
 	}