Fix null accesses on field.access.*

[Speedphoenix]

This happens at least when the constructor is not overridden (and the null access did not provide useful context)

From what I can tell, usually field.access is not null (but can be an empty array), but this yields null:

var f = (macro class {
    function new() {
    }
}).fields[0];
trace(f.access);

And the documentation does list it as nullable