Revert default password setting & using "HiddenString" even for empty strings

src/Core/Config/Cache/ConfigCache.php

@@ -95,7 +95,7 @@ class ConfigCache implements IConfigCache, IPConfigCache
 
 		if ($this->hidePasswordOutput &&
 		    $key == 'password' &&
-		    !empty($value) && is_string($value)) {
+		    is_string($value)) {
 			$this->config[$cat][$key] = new HiddenString((string) $value);
 		} else {
 			$this->config[$cat][$key] = $value;