Which branch of imgui should we use?

I tried to checkout imgui/master and had some compile errors. I fixed those but I'm getting a runtime crash saying:
Assertion failed: (GImGui != __null && "No current context. Did you call ImGui::CreateContext() or ImGui::SetCurrentContext()?"), function GetIO,

I'll keep debugging, but maybe there's a quick fix you know of.
Thanks for the cool project!
