Pass AJXP_VALUE_CLEAR as metadata value to force clearing key after array_merge()

Author: cdujeu

core/src/plugins/metastore.serial/class.SerialMetaStore.php

@@ -74,6 +74,11 @@ public function setMetadata($ajxpNode, $nameSpace, $metaData, $private = false,
             self::$metaCache[$nameSpace] = array();
         }
         self::$metaCache[$nameSpace] = array_merge(self::$metaCache[$nameSpace], $metaData);
+        if(is_array(self::$metaCache[$nameSpace])){
+            foreach(self::$metaCache[$nameSpace] as $k => $v){
+                if($v == AJXP_VALUE_CLEAR) unset(self::$metaCache[$nameSpace][$k]);
+            }
+        }
         $this->saveMetaFileData(
             $ajxpNode,
             $scope,