BeginPopupContextItem(): Skip processing when SkipItems is set as LastItemId is unreliable and we assert when it is zero. + Minor comments on columns.
BeginPopupContextItem(): Skip processing when SkipItems is set as LastItemId is unreliable and we assert when it is zero. + Minor comments on columns.

burningreggae/imgui,Flix01/imgui,aimotive/imgui-glfw,dougbinks/imgui,ggtucker/imgui,ocornut/imgui,burningreggae/imgui,bkaradzic/imgui,Flix01/imgui,cmaughan/imgui,nProtect/imgui,aimotive/imgui-glfw,dougbinks/imgui,ggtucker/imgui,cmaughan/imgui,ocornut/imgui,nProtect/imgui,bkaradzic/imgui,ggtucker/imgui,cmaughan/imgui,nProtect/imgui,bkaradzic/imgui,Flix01/imgui,cmaughan/imgui,ocornut/imgui