message: only fetch tables if we have a schema, otherwise reset options.
diff: @@ -65,7 +65,7 @@ ${this.props.queryEditor.schema}/${input}`;
  }
  // TODO: move fetching methods to the actions.
  fetchTables(dbId, schema, substr) {
  - if (dbId) {
  + if (dbId && schema) {
  this.setState({ tableLoading: true, tableOptions: [] });
  const url = `/superset/tables/${dbId}/${schema}/${substr}/`;
  $.get(url, (data) => {
  @@ -75,6 +75,8 @@ ${this.props.queryEditor.schema}/${input}`;
  tableLength: data.tableLength,
  });
  });
  + } else {
  + this.setState({ tableLoading: false, tableOptions: [] });
  }
  }
  changeTable(tableOpt) {
  