SelectFile library generates a “FATAL EXCEPTION: main” error

OK just heading home in a sec ill look into it.

Ok thats because you have to make use of a third party file manager.
On google play store the File Manager: free and easily by Xiaomi inc is the one I use. This will allow you to select a file with your sketch.
The folder selector is able to make use of the default file manager, but not the file selector. I cant remember if this is recent or has always been this way. In any case you should now be able to load your file.

Thanks I will give it a try.