How to select the current frame using jsfl?

I have a code that selects the current frame as follows:

var dom = fl.getDocumentDOM().getTimeline();
var currentFrame = dom.currentFrame;
dom.setSelectedFrames(currentFrame, currentFrame);

This is a normal executable command, but when I had to use MMExecute to execute this command in swf, an error inevitably occurred.

When a symbol is selected, all frames in which the symbol is located will be selected. At this time, the command will be invalid.
Unfortunately, I have to select the symbol before executing subsequent commands.

I tried several methods and still could not solve it. I need some help, thanks.