Merge pull request #33276 from thersane-john/fix_20.0_default_setup_default_value

Fix setup default value

Author: eldy

htdocs/core/class/html.formsetup.class.php

@@ -615,7 +615,7 @@ class FormSetupItem
 	/** @var string $picto */
 	public $picto = '';
 
-	/** @var string $fieldValue */
+	/** @var string|null $fieldValue */
 	public $fieldValue;
 
 	/** @var string $defaultFieldValue */
@@ -700,10 +700,10 @@ public function loadValueFromConf()
 	{
 		global $conf;
 		if (isset($conf->global->{$this->confKey})) {
-			$this->fieldValue = getDolGlobalString($this->confKey);
+			$this->fieldValue = getDolGlobalString($this->confKey, null);
 			return true;
 		} else {
-			$this->fieldValue = '';
+			$this->fieldValue = null;
 			return false;
 		}
 	}