handleVisDoubleClickEvent(properties) {
    if (properties.nodes.length || properties.edges.length) {
      if (this.editorMode || !utils.isTrue($tm.config.sys.singleClickMode)) {
        this.handleOpenMapElementEvent(properties);
      }
    } else { // = clicked on an empty spot
      if (this.editorMode) {
        this.handleInsertNode(properties.pointer.canvas);
      }
    }
  }
This handler is registered at and called by the vis network event
system.

@see Coordinates not passed on click/tap events within the properties object
@see https://github.com/almende/vis/issues/440

@properties a list of nodes and/or edges that correspond to the
click event.