Fix missing attribute connection in VLayerConnector during init

This fix initialize the two variabiles connection and _uri in VLayerConnector as it is implemented in all the other db_plugins. This fix avoid a crash when __del__ is called in the class DBConnector that check is connection is null which does not exist in VLayerConnector.

python/plugins/db_manager/db_plugins/vlayers/connector.py

@@ -112,6 +112,8 @@ class VLayerRegistry:
 class VLayerConnector(DBConnector):
 
     def __init__(self, uri):
+        DBConnector.__init__(self, uri)
+        
         self.mapSridToName = {}
 
     def _execute(self, cursor, sql):