Attempt to please phpstan.

src/Core/InstanceConfigTrait.php

@@ -192,7 +192,7 @@ trait InstanceConfigTrait
      *
      * The config value for this key must exist, it can never be null.
      *
-     * @param string $key The key to get.
+     * @param string|null $key The key to get.
      * @return mixed Configuration data at the named key
      * @throws \InvalidArgumentException
      */

src/Core/StaticConfigTrait.php

@@ -181,7 +181,7 @@ trait StaticConfigTrait
      *
      * The config value for this key must exist, it can never be null.
      *
-     * @param string $key The name of the configuration.
+     * @param string|null $key The name of the configuration.
      * @return mixed Configuration data at the named key.
      * @throws \InvalidArgumentException If value does not exist.
      */