Metrics: Fix not being able to expand "ParentWindow" when parent window is same as root window.
Metrics: Fix not being able to expand "ParentWindow" when parent window is same as root window.

aimotive/imgui-glfw,Flix01/imgui,ggtucker/imgui,ggtucker/imgui,ggtucker/imgui,nProtect/imgui,ocornut/imgui,nProtect/imgui,bkaradzic/imgui,bkaradzic/imgui,ocornut/imgui,Flix01/imgui,Flix01/imgui,nProtect/imgui,aimotive/imgui-glfw,ocornut/imgui,bkaradzic/imgui