`Julia: Execute File` doesn't recognize a module

[aviatesk]

MRE would be to invoke this command for e.g. VSCodeServer/src/trees.jl.
I tracked down this is because this commands uses vscode.Position(0, 0) for the current position in a document and get_expr return nothing for this case and so finally getModuleForEditor always returns Main for that case.

The super easy fix is to change the default position into vscode.Position(0, 1) or whatever, but that won't be ideal, taking an empty editor into consideration.
Maybe @ZacLN do you have an idea to fix this case ? If it's not easy to fix, I think we can go with the easy way for now.

[pfitzseb]

That's basically julia-vscode/LanguageServer.jl#771, I think. Unless we can get a quick fix for that, let's go with document.validatePosition(vscode.Position(0, 1)), imho.