Fix to allow using SetNextWindow* functions with ImGuiSetCond_Appearing on modal windows (#377)
Fix to allow using SetNextWindow* functions with ImGuiSetCond_Appearing on modal windows (#377)

Also affect other popups which called FindBestPopupWindowPos() on their
second frame but it most often acts as a no-op but it wouldn't be
noticeable.

bkaradzic/imgui,seanmiddleditch/imgui,Flix01/imgui,bkaradzic/imgui,cmaughan/imgui,Flix01/imgui,ocornut/imgui,thevaber/imgui,Psybrus/imgui,rxantos/imgui,ggtucker/imgui,Pagghiu/imgui,burningreggae/imgui,ocornut/imgui,nProtect/imgui,bkaradzic/imgui,nmlgc/imgui,emoon/imgui,wasikuss/imgui,Psybrus/imgui,mikesart/imgui,usagi/imguixx,kylawl/imgui,ggtucker/imgui,wflohry/imgui-addons,tom-seddon/imgui,seanmiddleditch/imgui,elect86/imgui,kylawl/imgui,mikesart/imgui,cmaughan/imgui,cmaughan/imgui,nProtect/imgui,dougbinks/imgui,burningreggae/imgui,aimotive/imgui-glfw,rxantos/imgui,thevaber/imgui,tom-seddon/imgui,ocornut/imgui,ggtucker/imgui,wflohry/imgui-addons,dougbinks/imgui,nProtect/imgui,nmlgc/imgui,aimotive/imgui-glfw,usagi/imguixx,emoon/imgui,elect86/imgui,wasikuss/imgui,thennequin/imgui,Pagghiu/imgui,Flix01/imgui,thennequin/imgui,cmaughan/imgui