Why error in importing external edge color and size under Visualization->Edges->Size and color->External?

[Bennylikescoding]

Hi everyone! I've been working on this issue for two days but don't know how to fix it.
Here is my "external edge color and size" file (in txt format separated by space), sure for test, this file contains only 1 row besides the header :

The error says:

In English, it reads, "Error in $<-.data.frame: replacement has 0 row, data has 1".

I googled the error message almost everywhere on stackoverflow and many other websites but still don't know how to fix it.

I've also tried my best to retrieve the record but I don't know where the numbers before the information is, i.e., "91: stop","90:$<-.data.frame", etc, because they are not in muxVizGUI.R, not in server.R, not in ui.R, etc, thus, I cannot fix the problem according to the warning message.

At one time I thought it may be the wrong sequence to import the data before rendering the graph, I've tried:

1. Apply layout-> import my external edges files ->Render network;
2. import my external edges files ->Apply layout->Render network;

But neither of them works since the upload procedure is OK, but always fail in "import" procedure, as prompted by the lower right pop-up info messages.

Does anyone know how to fix the problem? I appreciate any of your help and thanks a lot!