Focus: Child inherit focus scope from parent (amend 2ebe08be).

imgui.cpp

@@ -5950,7 +5950,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         window->DC.NavLayerCurrentMask = (1 << ImGuiNavLayer_Main);
         window->DC.NavLayerActiveMask = window->DC.NavLayerActiveMaskNext;
         window->DC.NavLayerActiveMaskNext = 0x00;
-        window->DC.NavFocusScopeIdCurrent = 0;
+        window->DC.NavFocusScopeIdCurrent = parent_window ? parent_window->DC.NavFocusScopeIdCurrent : 0;
         window->DC.NavHideHighlightOneFrame = false;
         window->DC.NavHasScroll = (window->ScrollMax.y > 0.0f);