add_arrow does not support geocoded file in plot_transections.py

https://github.com/insarlab/MintPy/blob/5405746ed87bb7f8854ee8d7560173099864a40c/mintpy/plot_transection.py#L324

This line gives an error message when working with geocoded files.

Also when using interactive graphics with plot_transections.py, zooming in at one location counted as one click.