Tests fail on julia 1.2

[davidanthoff]

https://travis-ci.org/julia-vscode/LanguageServer.jl/jobs/560588597

Unclear to me what is going on there...

[JeffBezanson]

I think I figured this out. In SymbolServer, from_static_init.jl:158:

                elseif !(isempty(t.types) || Base.isvatuple(t)) || t.mutable
                        out.vals[String(n)] = structStore(string.(p),
                                                     collect(string.(fieldnames(t))),
                                                     string.(collect(t.types)),
                                                     read_methods(x),
                                                     _getdoc(x))

t.types is not always defined. Should use fieldtypes instead.