QueryID not cleared when calling close()

The following procedure causes an issue:
1) Create a new DB_MYSQL instance
2) Make a call to query()
3) Make a call to close()
4) Make another call to query()

Line 219 still sees a QueryID as existing so when it calls warnings(), Line 401 causes an error because LinkID is false and mysqli_warning_count is not expecting a boolean parameter.

classes/mysql.class.php

@@ -291,6 +291,7 @@ function close() {
 				$this->halt('Cannot close connection or connection did not open.');
 			}
 			$this->LinkID = false;
+			$this->QueryID = false;
 		}
 	}